diff --git a/shared/static/scripts/sx-test-runner.js b/shared/static/scripts/sx-test-runner.js
index 89ce30c..2705255 100644
--- a/shared/static/scripts/sx-test-runner.js
+++ b/shared/static/scripts/sx-test-runner.js
@@ -1,5 +1,5 @@
-// sx-test-runner.js — Run test.sx in the browser using sx-browser.js.
-// Loaded on the /specs/testing page. Uses the Sx global.
+// sx-test-runner.js — Run SX test specs in the browser using sx-browser.js.
+// Supports both legacy (monolithic test.sx) and modular (per-spec) modes.
 (function() {
   var NIL = Sx.NIL;
   function isNil(x) { return x === NIL || x === null || x === undefined; }
@@ -21,13 +21,9 @@
     return false;
   }
 
-  window.sxRunTests = function(srcId, outId, btnId) {
-    var src = document.getElementById(srcId).textContent;
-    var out = document.getElementById(outId);
-    var btn = document.getElementById(btnId);
-
+  // --- Platform functions shared across all specs ---
+  function makeEnv() {
     var stack = [], passed = 0, failed = 0, num = 0, lines = [];
-
     var env = {
       "try-call": function(thunk) {
         try {
@@ -49,6 +45,7 @@
       "push-suite": function(name) { stack.push(name); },
       "pop-suite": function() { stack.pop(); },
 
+      // Primitives that sx-browser.js may not expose in env
       "equal?": function(a, b) { return deepEqual(a, b); },
       "eq?": function(a, b) { return a === b; },
       "boolean?": function(x) { return typeof x === "boolean"; },
@@ -68,28 +65,159 @@
       },
       "has-key?": function(d, k) { return d && typeof d === "object" && k in d; },
       "append": function(c, x) { return Array.isArray(x) ? (c||[]).concat(x) : (c||[]).concat([x]); },
+      "for-each-indexed": function(f, coll) {
+        for (var i = 0; i < (coll||[]).length; i++) Sx.eval([f, i, coll[i]], env);
+      },
+      "for-each": function(f, coll) {
+        for (var i = 0; i < (coll||[]).length; i++) Sx.eval([f, coll[i]], env);
+      },
+      "dict-set!": function(d, k, v) { if (d) d[k] = v; },
+      "dict-has?": function(d, k) { return d && typeof d === "object" && k in d; },
+      "dict-get": function(d, k) { return d ? d[k] : undefined; },
+      "starts-with?": function(s, prefix) { return String(s).indexOf(prefix) === 0; },
+      "ends-with?": function(s, suffix) { var str = String(s); return str.indexOf(suffix) === str.length - suffix.length; },
+      "slice": function(s, start, end) { return end !== undefined ? s.slice(start, end) : s.slice(start); },
+      "inc": function(n) { return n + 1; },
+      "append!": function(arr, item) { if (Array.isArray(arr)) arr.push(item); },
+      "dict": function() { return {}; },
+
+      // --- Parser platform functions ---
+      "sx-parse": function(source) { return Sx.parseAll(source); },
+      "sx-serialize": function(val) {
+        if (val === NIL || val === null || val === undefined) return "nil";
+        if (typeof val === "boolean") return val ? "true" : "false";
+        if (typeof val === "number") return String(val);
+        if (typeof val === "string") return '"' + val.replace(/\\/g, "\\\\").replace(/"/g, '\\"') + '"';
+        if (val && (val._sym || val._sx_symbol)) return val.name;
+        if (val && (val._kw || val._sx_keyword)) return ":" + val.name;
+        if (Array.isArray(val)) return "(" + val.map(function(x) { return env["sx-serialize"](x); }).join(" ") + ")";
+        if (val && typeof val === "object") {
+          var parts = [];
+          Object.keys(val).forEach(function(k) { parts.push(":" + k); parts.push(env["sx-serialize"](val[k])); });
+          return "{" + parts.join(" ") + "}";
+        }
+        return String(val);
+      },
+      "make-symbol": function(name) { return Sx.sym ? Sx.sym(name) : { _sx_symbol: true, name: name, toString: function() { return name; } }; },
+      "make-keyword": function(name) { return Sx.kw ? Sx.kw(name) : { _sx_keyword: true, name: name, toString: function() { return name; } }; },
+      "symbol-name": function(s) { return s && s.name ? s.name : String(s); },
+      "keyword-name": function(k) { return k && k.name ? k.name : String(k); },
+
+      // --- Render platform function ---
+      "render-html": function(sxSource) {
+        if (!Sx.renderToHtml) throw new Error("render-to-html not available");
+        var exprs = Sx.parseAll(sxSource);
+        var result = "";
+        for (var i = 0; i < exprs.length; i++) result += Sx.renderToHtml(exprs[i], env);
+        return result;
+      },
     };
+    return { env: env, getResults: function() { return { passed: passed, failed: failed, num: num, lines: lines }; } };
+  }
+
+  function evalSource(src, env) {
+    var exprs = Sx.parseAll(src);
+    for (var i = 0; i < exprs.length; i++) Sx.eval(exprs[i], env);
+  }
+
+  function loadRouterFromBootstrap(env) {
+    if (Sx.splitPathSegments) {
+      env["split-path-segments"] = Sx.splitPathSegments;
+      env["parse-route-pattern"] = Sx.parseRoutePattern;
+      env["match-route-segments"] = Sx.matchRouteSegments;
+      env["match-route"] = Sx.matchRoute;
+      env["find-matching-route"] = Sx.findMatchingRoute;
+      env["make-route-segment"] = Sx.makeRouteSegment;
+    }
+  }
+
+  // --- Legacy runner (monolithic test.sx) ---
+  window.sxRunTests = function(srcId, outId, btnId) {
+    var src = document.getElementById(srcId).textContent;
+    var out = document.getElementById(outId);
+    var btn = document.getElementById(btnId);
+    var ctx = makeEnv();
 
     try {
       var t0 = performance.now();
-      var exprs = Sx.parseAll(src);
-      for (var i = 0; i < exprs.length; i++) Sx.eval(exprs[i], env);
+      evalSource(src, ctx.env);
       var elapsed = Math.round(performance.now() - t0);
-      lines.push("");
-      lines.push("1.." + num);
-      lines.push("# tests " + (passed + failed));
-      lines.push("# pass  " + passed);
-      if (failed > 0) lines.push("# fail  " + failed);
-      lines.push("# time  " + elapsed + "ms");
+      var r = ctx.getResults();
+      r.lines.push("");
+      r.lines.push("1.." + r.num);
+      r.lines.push("# tests " + (r.passed + r.failed));
+      r.lines.push("# pass  " + r.passed);
+      if (r.failed > 0) r.lines.push("# fail  " + r.failed);
+      r.lines.push("# time  " + elapsed + "ms");
     } catch(e) {
-      lines.push("");
-      lines.push("FATAL: " + (e.message || String(e)));
+      var r = ctx.getResults();
+      r.lines.push("");
+      r.lines.push("FATAL: " + (e.message || String(e)));
     }
 
-    out.textContent = lines.join("\n");
+    out.textContent = r.lines.join("\n");
     out.style.display = "block";
-    btn.textContent = passed + "/" + (passed + failed) + " passed" + (failed === 0 ? "" : " (" + failed + " failed)");
-    btn.className = failed > 0
+    btn.textContent = r.passed + "/" + (r.passed + r.failed) + " passed" + (r.failed === 0 ? "" : " (" + r.failed + " failed)");
+    btn.className = r.failed > 0
+      ? "px-4 py-2 rounded-md bg-red-600 text-white font-medium text-sm cursor-default"
+      : "px-4 py-2 rounded-md bg-green-600 text-white font-medium text-sm cursor-default";
+  };
+
+  // --- Modular runner (per-spec or all) ---
+  var SPECS = {
+    "eval":   { needs: [] },
+    "parser": { needs: ["sx-parse"] },
+    "router": { needs: [] },
+    "render": { needs: ["render-html"] },
+  };
+
+  window.sxRunModularTests = function(specName, outId, btnId) {
+    var out = document.getElementById(outId);
+    var btn = document.getElementById(btnId);
+    var ctx = makeEnv();
+    var specs = specName === "all" ? Object.keys(SPECS) : [specName];
+
+    try {
+      var t0 = performance.now();
+
+      // Load framework
+      var fwEl = document.getElementById("test-framework-source");
+      if (fwEl) {
+        evalSource(fwEl.textContent, ctx.env);
+      }
+
+      for (var si = 0; si < specs.length; si++) {
+        var sn = specs[si];
+        if (!SPECS[sn]) continue;
+
+        // Load router from bootstrap if needed
+        if (sn === "router") loadRouterFromBootstrap(ctx.env);
+
+        // Find spec source — either per-spec textarea or embedded in overview
+        var specEl = document.getElementById("test-spec-" + sn);
+        if (specEl) {
+          evalSource(specEl.textContent, ctx.env);
+        }
+      }
+
+      var elapsed = Math.round(performance.now() - t0);
+      var r = ctx.getResults();
+      r.lines.push("");
+      r.lines.push("1.." + r.num);
+      r.lines.push("# tests " + (r.passed + r.failed));
+      r.lines.push("# pass  " + r.passed);
+      if (r.failed > 0) r.lines.push("# fail  " + r.failed);
+      r.lines.push("# time  " + elapsed + "ms");
+    } catch(e) {
+      var r = ctx.getResults();
+      r.lines.push("");
+      r.lines.push("FATAL: " + (e.message || String(e)));
+    }
+
+    out.textContent = r.lines.join("\n");
+    out.style.display = "block";
+    btn.textContent = r.passed + "/" + (r.passed + r.failed) + " passed" + (r.failed === 0 ? "" : " (" + r.failed + " failed)");
+    btn.className = r.failed > 0
       ? "px-4 py-2 rounded-md bg-red-600 text-white font-medium text-sm cursor-default"
       : "px-4 py-2 rounded-md bg-green-600 text-white font-medium text-sm cursor-default";
   };
diff --git a/shared/sx/ref/test-eval.sx b/shared/sx/ref/test-eval.sx
new file mode 100644
index 0000000..06f655f
--- /dev/null
+++ b/shared/sx/ref/test-eval.sx
@@ -0,0 +1,494 @@
+;; ==========================================================================
+;; test-eval.sx — Tests for the core evaluator and primitives
+;;
+;; Requires: test-framework.sx loaded first.
+;; Modules tested: eval.sx, primitives.sx
+;; ==========================================================================
+
+
+;; --------------------------------------------------------------------------
+;; Literals and types
+;; --------------------------------------------------------------------------
+
+(defsuite "literals"
+  (deftest "numbers are numbers"
+    (assert-type "number" 42)
+    (assert-type "number" 3.14)
+    (assert-type "number" -1))
+
+  (deftest "strings are strings"
+    (assert-type "string" "hello")
+    (assert-type "string" ""))
+
+  (deftest "booleans are booleans"
+    (assert-type "boolean" true)
+    (assert-type "boolean" false))
+
+  (deftest "nil is nil"
+    (assert-type "nil" nil)
+    (assert-nil nil))
+
+  (deftest "lists are lists"
+    (assert-type "list" (list 1 2 3))
+    (assert-type "list" (list)))
+
+  (deftest "dicts are dicts"
+    (assert-type "dict" {:a 1 :b 2})))
+
+
+;; --------------------------------------------------------------------------
+;; Arithmetic
+;; --------------------------------------------------------------------------
+
+(defsuite "arithmetic"
+  (deftest "addition"
+    (assert-equal 3 (+ 1 2))
+    (assert-equal 0 (+ 0 0))
+    (assert-equal -1 (+ 1 -2))
+    (assert-equal 10 (+ 1 2 3 4)))
+
+  (deftest "subtraction"
+    (assert-equal 1 (- 3 2))
+    (assert-equal -1 (- 2 3)))
+
+  (deftest "multiplication"
+    (assert-equal 6 (* 2 3))
+    (assert-equal 0 (* 0 100))
+    (assert-equal 24 (* 1 2 3 4)))
+
+  (deftest "division"
+    (assert-equal 2 (/ 6 3))
+    (assert-equal 2.5 (/ 5 2)))
+
+  (deftest "modulo"
+    (assert-equal 1 (mod 7 3))
+    (assert-equal 0 (mod 6 3))))
+
+
+;; --------------------------------------------------------------------------
+;; Comparison
+;; --------------------------------------------------------------------------
+
+(defsuite "comparison"
+  (deftest "equality"
+    (assert-true (= 1 1))
+    (assert-false (= 1 2))
+    (assert-true (= "a" "a"))
+    (assert-false (= "a" "b")))
+
+  (deftest "deep equality"
+    (assert-true (equal? (list 1 2 3) (list 1 2 3)))
+    (assert-false (equal? (list 1 2) (list 1 3)))
+    (assert-true (equal? {:a 1} {:a 1}))
+    (assert-false (equal? {:a 1} {:a 2})))
+
+  (deftest "ordering"
+    (assert-true (< 1 2))
+    (assert-false (< 2 1))
+    (assert-true (> 2 1))
+    (assert-true (<= 1 1))
+    (assert-true (<= 1 2))
+    (assert-true (>= 2 2))
+    (assert-true (>= 3 2))))
+
+
+;; --------------------------------------------------------------------------
+;; String operations
+;; --------------------------------------------------------------------------
+
+(defsuite "strings"
+  (deftest "str concatenation"
+    (assert-equal "abc" (str "a" "b" "c"))
+    (assert-equal "hello world" (str "hello" " " "world"))
+    (assert-equal "42" (str 42))
+    (assert-equal "" (str)))
+
+  (deftest "string-length"
+    (assert-equal 5 (string-length "hello"))
+    (assert-equal 0 (string-length "")))
+
+  (deftest "substring"
+    (assert-equal "ell" (substring "hello" 1 4))
+    (assert-equal "hello" (substring "hello" 0 5)))
+
+  (deftest "string-contains?"
+    (assert-true (string-contains? "hello world" "world"))
+    (assert-false (string-contains? "hello" "xyz")))
+
+  (deftest "upcase and downcase"
+    (assert-equal "HELLO" (upcase "hello"))
+    (assert-equal "hello" (downcase "HELLO")))
+
+  (deftest "trim"
+    (assert-equal "hello" (trim "  hello  "))
+    (assert-equal "hello" (trim "hello")))
+
+  (deftest "split and join"
+    (assert-equal (list "a" "b" "c") (split "a,b,c" ","))
+    (assert-equal "a-b-c" (join "-" (list "a" "b" "c")))))
+
+
+;; --------------------------------------------------------------------------
+;; List operations
+;; --------------------------------------------------------------------------
+
+(defsuite "lists"
+  (deftest "constructors"
+    (assert-equal (list 1 2 3) (list 1 2 3))
+    (assert-equal (list) (list))
+    (assert-length 3 (list 1 2 3)))
+
+  (deftest "first and rest"
+    (assert-equal 1 (first (list 1 2 3)))
+    (assert-equal (list 2 3) (rest (list 1 2 3)))
+    (assert-nil (first (list)))
+    (assert-equal (list) (rest (list))))
+
+  (deftest "nth"
+    (assert-equal 1 (nth (list 1 2 3) 0))
+    (assert-equal 2 (nth (list 1 2 3) 1))
+    (assert-equal 3 (nth (list 1 2 3) 2)))
+
+  (deftest "last"
+    (assert-equal 3 (last (list 1 2 3)))
+    (assert-nil (last (list))))
+
+  (deftest "cons and append"
+    (assert-equal (list 0 1 2) (cons 0 (list 1 2)))
+    (assert-equal (list 1 2 3 4) (append (list 1 2) (list 3 4))))
+
+  (deftest "reverse"
+    (assert-equal (list 3 2 1) (reverse (list 1 2 3)))
+    (assert-equal (list) (reverse (list))))
+
+  (deftest "empty?"
+    (assert-true (empty? (list)))
+    (assert-false (empty? (list 1))))
+
+  (deftest "len"
+    (assert-equal 0 (len (list)))
+    (assert-equal 3 (len (list 1 2 3))))
+
+  (deftest "contains?"
+    (assert-true (contains? (list 1 2 3) 2))
+    (assert-false (contains? (list 1 2 3) 4)))
+
+  (deftest "flatten"
+    (assert-equal (list 1 2 3 4) (flatten (list (list 1 2) (list 3 4))))))
+
+
+;; --------------------------------------------------------------------------
+;; Dict operations
+;; --------------------------------------------------------------------------
+
+(defsuite "dicts"
+  (deftest "dict literal"
+    (assert-type "dict" {:a 1 :b 2})
+    (assert-equal 1 (get {:a 1} "a"))
+    (assert-equal 2 (get {:a 1 :b 2} "b")))
+
+  (deftest "assoc"
+    (assert-equal {:a 1 :b 2} (assoc {:a 1} "b" 2))
+    (assert-equal {:a 99} (assoc {:a 1} "a" 99)))
+
+  (deftest "dissoc"
+    (assert-equal {:b 2} (dissoc {:a 1 :b 2} "a")))
+
+  (deftest "keys and vals"
+    (let ((d {:a 1 :b 2}))
+      (assert-length 2 (keys d))
+      (assert-length 2 (vals d))
+      (assert-contains "a" (keys d))
+      (assert-contains "b" (keys d))))
+
+  (deftest "has-key?"
+    (assert-true (has-key? {:a 1} "a"))
+    (assert-false (has-key? {:a 1} "b")))
+
+  (deftest "merge"
+    (assert-equal {:a 1 :b 2 :c 3}
+      (merge {:a 1 :b 2} {:c 3}))
+    (assert-equal {:a 99 :b 2}
+      (merge {:a 1 :b 2} {:a 99}))))
+
+
+;; --------------------------------------------------------------------------
+;; Predicates
+;; --------------------------------------------------------------------------
+
+(defsuite "predicates"
+  (deftest "nil?"
+    (assert-true (nil? nil))
+    (assert-false (nil? 0))
+    (assert-false (nil? false))
+    (assert-false (nil? "")))
+
+  (deftest "number?"
+    (assert-true (number? 42))
+    (assert-true (number? 3.14))
+    (assert-false (number? "42")))
+
+  (deftest "string?"
+    (assert-true (string? "hello"))
+    (assert-false (string? 42)))
+
+  (deftest "list?"
+    (assert-true (list? (list 1 2)))
+    (assert-false (list? "not a list")))
+
+  (deftest "dict?"
+    (assert-true (dict? {:a 1}))
+    (assert-false (dict? (list 1))))
+
+  (deftest "boolean?"
+    (assert-true (boolean? true))
+    (assert-true (boolean? false))
+    (assert-false (boolean? nil))
+    (assert-false (boolean? 0)))
+
+  (deftest "not"
+    (assert-true (not false))
+    (assert-true (not nil))
+    (assert-false (not true))
+    (assert-false (not 1))
+    (assert-false (not "x"))))
+
+
+;; --------------------------------------------------------------------------
+;; Special forms
+;; --------------------------------------------------------------------------
+
+(defsuite "special-forms"
+  (deftest "if"
+    (assert-equal "yes" (if true "yes" "no"))
+    (assert-equal "no" (if false "yes" "no"))
+    (assert-equal "no" (if nil "yes" "no"))
+    (assert-nil (if false "yes")))
+
+  (deftest "when"
+    (assert-equal "yes" (when true "yes"))
+    (assert-nil (when false "yes")))
+
+  (deftest "cond"
+    (assert-equal "a" (cond true "a" :else "b"))
+    (assert-equal "b" (cond false "a" :else "b"))
+    (assert-equal "c" (cond
+                        false "a"
+                        false "b"
+                        :else "c")))
+
+  (deftest "and"
+    (assert-true (and true true))
+    (assert-false (and true false))
+    (assert-false (and false true))
+    (assert-equal 3 (and 1 2 3)))
+
+  (deftest "or"
+    (assert-equal 1 (or 1 2))
+    (assert-equal 2 (or false 2))
+    (assert-equal "fallback" (or nil false "fallback"))
+    (assert-false (or false false)))
+
+  (deftest "let"
+    (assert-equal 3 (let ((x 1) (y 2)) (+ x y)))
+    (assert-equal "hello world"
+      (let ((a "hello") (b " world")) (str a b))))
+
+  (deftest "let clojure-style"
+    (assert-equal 3 (let (x 1 y 2) (+ x y))))
+
+  (deftest "do / begin"
+    (assert-equal 3 (do 1 2 3))
+    (assert-equal "last" (begin "first" "middle" "last")))
+
+  (deftest "define"
+    (define x 42)
+    (assert-equal 42 x))
+
+  (deftest "set!"
+    (define x 1)
+    (set! x 2)
+    (assert-equal 2 x)))
+
+
+;; --------------------------------------------------------------------------
+;; Lambda and closures
+;; --------------------------------------------------------------------------
+
+(defsuite "lambdas"
+  (deftest "basic lambda"
+    (let ((add (fn (a b) (+ a b))))
+      (assert-equal 3 (add 1 2))))
+
+  (deftest "closure captures env"
+    (let ((x 10))
+      (let ((add-x (fn (y) (+ x y))))
+        (assert-equal 15 (add-x 5)))))
+
+  (deftest "lambda as argument"
+    (assert-equal (list 2 4 6)
+      (map (fn (x) (* x 2)) (list 1 2 3))))
+
+  (deftest "recursive lambda via define"
+    (define factorial
+      (fn (n) (if (<= n 1) 1 (* n (factorial (- n 1))))))
+    (assert-equal 120 (factorial 5)))
+
+  (deftest "higher-order returns lambda"
+    (let ((make-adder (fn (n) (fn (x) (+ n x)))))
+      (let ((add5 (make-adder 5)))
+        (assert-equal 8 (add5 3))))))
+
+
+;; --------------------------------------------------------------------------
+;; Higher-order forms
+;; --------------------------------------------------------------------------
+
+(defsuite "higher-order"
+  (deftest "map"
+    (assert-equal (list 2 4 6)
+      (map (fn (x) (* x 2)) (list 1 2 3)))
+    (assert-equal (list) (map (fn (x) x) (list))))
+
+  (deftest "filter"
+    (assert-equal (list 2 4)
+      (filter (fn (x) (= (mod x 2) 0)) (list 1 2 3 4)))
+    (assert-equal (list)
+      (filter (fn (x) false) (list 1 2 3))))
+
+  (deftest "reduce"
+    (assert-equal 10 (reduce (fn (acc x) (+ acc x)) 0 (list 1 2 3 4)))
+    (assert-equal 0 (reduce (fn (acc x) (+ acc x)) 0 (list))))
+
+  (deftest "some"
+    (assert-true (some (fn (x) (> x 3)) (list 1 2 3 4 5)))
+    (assert-false (some (fn (x) (> x 10)) (list 1 2 3))))
+
+  (deftest "every?"
+    (assert-true (every? (fn (x) (> x 0)) (list 1 2 3)))
+    (assert-false (every? (fn (x) (> x 2)) (list 1 2 3))))
+
+  (deftest "map-indexed"
+    (assert-equal (list "0:a" "1:b" "2:c")
+      (map-indexed (fn (i x) (str i ":" x)) (list "a" "b" "c")))))
+
+
+;; --------------------------------------------------------------------------
+;; Components
+;; --------------------------------------------------------------------------
+
+(defsuite "components"
+  (deftest "defcomp creates component"
+    (defcomp ~test-comp (&key title)
+      (div title))
+    (assert-true (not (nil? ~test-comp))))
+
+  (deftest "component renders with keyword args"
+    (defcomp ~greeting (&key name)
+      (span (str "Hello, " name "!")))
+    (assert-true (not (nil? ~greeting))))
+
+  (deftest "component with children"
+    (defcomp ~box (&key &rest children)
+      (div :class "box" children))
+    (assert-true (not (nil? ~box))))
+
+  (deftest "component with default via or"
+    (defcomp ~label (&key text)
+      (span (or text "default")))
+    (assert-true (not (nil? ~label)))))
+
+
+;; --------------------------------------------------------------------------
+;; Macros
+;; --------------------------------------------------------------------------
+
+(defsuite "macros"
+  (deftest "defmacro creates macro"
+    (defmacro unless (cond &rest body)
+      `(if (not ,cond) (do ,@body)))
+    (assert-equal "yes" (unless false "yes"))
+    (assert-nil (unless true "no")))
+
+  (deftest "quasiquote and unquote"
+    (let ((x 42))
+      (assert-equal (list 1 42 3) `(1 ,x 3))))
+
+  (deftest "splice-unquote"
+    (let ((xs (list 2 3 4)))
+      (assert-equal (list 1 2 3 4 5) `(1 ,@xs 5)))))
+
+
+;; --------------------------------------------------------------------------
+;; Threading macro
+;; --------------------------------------------------------------------------
+
+(defsuite "threading"
+  (deftest "thread-first"
+    (assert-equal 8 (-> 5 (+ 1) (+ 2)))
+    (assert-equal "HELLO" (-> "hello" upcase))
+    (assert-equal "HELLO WORLD"
+      (-> "hello"
+          (str " world")
+          upcase))))
+
+
+;; --------------------------------------------------------------------------
+;; Truthiness
+;; --------------------------------------------------------------------------
+
+(defsuite "truthiness"
+  (deftest "truthy values"
+    (assert-true (if 1 true false))
+    (assert-true (if "x" true false))
+    (assert-true (if (list 1) true false))
+    (assert-true (if true true false)))
+
+  (deftest "falsy values"
+    (assert-false (if false true false))
+    (assert-false (if nil true false)))
+
+  ;; NOTE: empty list, zero, and empty string truthiness is
+  ;; platform-dependent. Python treats all three as falsy.
+  ;; JavaScript treats [] as truthy but 0 and "" as falsy.
+  ;; These tests are omitted — each bootstrapper should emit
+  ;; platform-specific truthiness tests instead.
+  )
+
+
+;; --------------------------------------------------------------------------
+;; Edge cases and regression tests
+;; --------------------------------------------------------------------------
+
+(defsuite "edge-cases"
+  (deftest "nested let scoping"
+    (let ((x 1))
+      (let ((x 2))
+        (assert-equal 2 x))
+      ;; outer x should be unchanged by inner let
+      ;; (this tests that let creates a new scope)
+      ))
+
+  (deftest "recursive map"
+    (assert-equal (list (list 2 4) (list 6 8))
+      (map (fn (sub) (map (fn (x) (* x 2)) sub))
+           (list (list 1 2) (list 3 4)))))
+
+  (deftest "keyword as value"
+    (assert-equal "class" :class)
+    (assert-equal "id" :id))
+
+  (deftest "dict with evaluated values"
+    (let ((x 42))
+      (assert-equal 42 (get {:val x} "val"))))
+
+  (deftest "nil propagation"
+    (assert-nil (get {:a 1} "missing"))
+    (assert-equal "default" (or (get {:a 1} "missing") "default")))
+
+  (deftest "empty operations"
+    (assert-equal (list) (map (fn (x) x) (list)))
+    (assert-equal (list) (filter (fn (x) true) (list)))
+    (assert-equal 0 (reduce (fn (acc x) (+ acc x)) 0 (list)))
+    (assert-equal 0 (len (list)))
+    (assert-equal "" (str))))
diff --git a/shared/sx/ref/test-framework.sx b/shared/sx/ref/test-framework.sx
new file mode 100644
index 0000000..21e5a10
--- /dev/null
+++ b/shared/sx/ref/test-framework.sx
@@ -0,0 +1,86 @@
+;; ==========================================================================
+;; test-framework.sx — Reusable test macros and assertion helpers
+;;
+;; Loaded first by all test runners. Provides deftest, defsuite, and
+;; assertion helpers. Requires 5 platform functions from the host:
+;;
+;;   try-call     (thunk)        -> {:ok true} | {:ok false :error "msg"}
+;;   report-pass  (name)         -> platform-specific pass output
+;;   report-fail  (name error)   -> platform-specific fail output
+;;   push-suite   (name)         -> push suite name onto context stack
+;;   pop-suite    ()             -> pop suite name from context stack
+;;
+;; Any host that provides these 5 functions can run any test spec.
+;; ==========================================================================
+
+
+;; --------------------------------------------------------------------------
+;; 1. Test framework macros
+;; --------------------------------------------------------------------------
+
+(defmacro deftest (name &rest body)
+  `(let ((result (try-call (fn () ,@body))))
+     (if (get result "ok")
+       (report-pass ,name)
+       (report-fail ,name (get result "error")))))
+
+(defmacro defsuite (name &rest items)
+  `(do (push-suite ,name)
+       ,@items
+       (pop-suite)))
+
+
+;; --------------------------------------------------------------------------
+;; 2. Assertion helpers — defined in SX, available in test bodies
+;; --------------------------------------------------------------------------
+
+(define assert-equal
+  (fn (expected actual)
+    (assert (equal? expected actual)
+      (str "Expected " (str expected) " but got " (str actual)))))
+
+(define assert-not-equal
+  (fn (a b)
+    (assert (not (equal? a b))
+      (str "Expected values to differ but both are " (str a)))))
+
+(define assert-true
+  (fn (val)
+    (assert val (str "Expected truthy but got " (str val)))))
+
+(define assert-false
+  (fn (val)
+    (assert (not val) (str "Expected falsy but got " (str val)))))
+
+(define assert-nil
+  (fn (val)
+    (assert (nil? val) (str "Expected nil but got " (str val)))))
+
+(define assert-type
+  (fn (expected-type val)
+    (let ((actual-type
+            (if (nil? val) "nil"
+              (if (boolean? val) "boolean"
+                (if (number? val) "number"
+                  (if (string? val) "string"
+                    (if (list? val) "list"
+                      (if (dict? val) "dict"
+                        "unknown"))))))))
+      (assert (= expected-type actual-type)
+        (str "Expected type " expected-type " but got " actual-type)))))
+
+(define assert-length
+  (fn (expected-len col)
+    (assert (= (len col) expected-len)
+      (str "Expected length " expected-len " but got " (len col)))))
+
+(define assert-contains
+  (fn (item col)
+    (assert (some (fn (x) (equal? x item)) col)
+      (str "Expected collection to contain " (str item)))))
+
+(define assert-throws
+  (fn (thunk)
+    (let ((result (try-call thunk)))
+      (assert (not (get result "ok"))
+        "Expected an error to be thrown but none was"))))
diff --git a/shared/sx/ref/test-parser.sx b/shared/sx/ref/test-parser.sx
new file mode 100644
index 0000000..57cc4a8
--- /dev/null
+++ b/shared/sx/ref/test-parser.sx
@@ -0,0 +1,222 @@
+;; ==========================================================================
+;; test-parser.sx — Tests for the SX parser and serializer
+;;
+;; Requires: test-framework.sx loaded first.
+;; Modules tested: parser.sx
+;;
+;; Platform functions required (beyond test framework):
+;;   sx-parse       (source)  -> list of AST expressions
+;;   sx-serialize   (expr)    -> SX source string
+;;   make-symbol    (name)    -> Symbol value
+;;   make-keyword   (name)    -> Keyword value
+;;   symbol-name    (sym)     -> string
+;;   keyword-name   (kw)      -> string
+;; ==========================================================================
+
+
+;; --------------------------------------------------------------------------
+;; Literal parsing
+;; --------------------------------------------------------------------------
+
+(defsuite "parser-literals"
+  (deftest "parse integers"
+    (assert-equal (list 42) (sx-parse "42"))
+    (assert-equal (list 0) (sx-parse "0"))
+    (assert-equal (list -7) (sx-parse "-7")))
+
+  (deftest "parse floats"
+    (assert-equal (list 3.14) (sx-parse "3.14"))
+    (assert-equal (list -0.5) (sx-parse "-0.5")))
+
+  (deftest "parse strings"
+    (assert-equal (list "hello") (sx-parse "\"hello\""))
+    (assert-equal (list "") (sx-parse "\"\"")))
+
+  (deftest "parse escape: newline"
+    (assert-equal (list "a\nb") (sx-parse "\"a\\nb\"")))
+
+  (deftest "parse escape: tab"
+    (assert-equal (list "a\tb") (sx-parse "\"a\\tb\"")))
+
+  (deftest "parse escape: quote"
+    (assert-equal (list "a\"b") (sx-parse "\"a\\\"b\"")))
+
+  (deftest "parse booleans"
+    (assert-equal (list true) (sx-parse "true"))
+    (assert-equal (list false) (sx-parse "false")))
+
+  (deftest "parse nil"
+    (assert-equal (list nil) (sx-parse "nil")))
+
+  (deftest "parse keywords"
+    (let ((result (sx-parse ":hello")))
+      (assert-length 1 result)
+      (assert-equal "hello" (keyword-name (first result)))))
+
+  (deftest "parse symbols"
+    (let ((result (sx-parse "foo")))
+      (assert-length 1 result)
+      (assert-equal "foo" (symbol-name (first result))))))
+
+
+;; --------------------------------------------------------------------------
+;; Composite parsing
+;; --------------------------------------------------------------------------
+
+(defsuite "parser-lists"
+  (deftest "parse empty list"
+    (let ((result (sx-parse "()")))
+      (assert-length 1 result)
+      (assert-equal (list) (first result))))
+
+  (deftest "parse list of numbers"
+    (let ((result (sx-parse "(1 2 3)")))
+      (assert-length 1 result)
+      (assert-equal (list 1 2 3) (first result))))
+
+  (deftest "parse nested lists"
+    (let ((result (sx-parse "(1 (2 3) 4)")))
+      (assert-length 1 result)
+      (assert-equal (list 1 (list 2 3) 4) (first result))))
+
+  (deftest "parse square brackets as list"
+    (let ((result (sx-parse "[1 2 3]")))
+      (assert-length 1 result)
+      (assert-equal (list 1 2 3) (first result))))
+
+  (deftest "parse mixed types"
+    (let ((result (sx-parse "(42 \"hello\" true nil)")))
+      (assert-length 1 result)
+      (let ((lst (first result)))
+        (assert-equal 42 (nth lst 0))
+        (assert-equal "hello" (nth lst 1))
+        (assert-equal true (nth lst 2))
+        (assert-nil (nth lst 3))))))
+
+
+;; --------------------------------------------------------------------------
+;; Dict parsing
+;; --------------------------------------------------------------------------
+
+(defsuite "parser-dicts"
+  (deftest "parse empty dict"
+    (let ((result (sx-parse "{}")))
+      (assert-length 1 result)
+      (assert-type "dict" (first result))))
+
+  (deftest "parse dict with keyword keys"
+    (let ((result (sx-parse "{:a 1 :b 2}")))
+      (assert-length 1 result)
+      (let ((d (first result)))
+        (assert-type "dict" d)
+        (assert-equal 1 (get d "a"))
+        (assert-equal 2 (get d "b")))))
+
+  (deftest "parse dict with string values"
+    (let ((result (sx-parse "{:name \"alice\"}")))
+      (assert-length 1 result)
+      (assert-equal "alice" (get (first result) "name")))))
+
+
+;; --------------------------------------------------------------------------
+;; Comments and whitespace
+;; --------------------------------------------------------------------------
+
+(defsuite "parser-whitespace"
+  (deftest "skip line comments"
+    (assert-equal (list 42) (sx-parse ";; comment\n42"))
+    (assert-equal (list 1 2) (sx-parse "1 ;; middle\n2")))
+
+  (deftest "skip whitespace"
+    (assert-equal (list 42) (sx-parse "  42  "))
+    (assert-equal (list 1 2) (sx-parse " 1 \n\t 2 ")))
+
+  (deftest "parse multiple top-level expressions"
+    (assert-length 3 (sx-parse "1 2 3"))
+    (assert-equal (list 1 2 3) (sx-parse "1 2 3")))
+
+  (deftest "empty input"
+    (assert-equal (list) (sx-parse "")))
+
+  (deftest "only comments"
+    (assert-equal (list) (sx-parse ";; just a comment\n;; another"))))
+
+
+;; --------------------------------------------------------------------------
+;; Quote sugar
+;; --------------------------------------------------------------------------
+
+(defsuite "parser-quote-sugar"
+  (deftest "quasiquote"
+    (let ((result (sx-parse "`foo")))
+      (assert-length 1 result)
+      (let ((expr (first result)))
+        (assert-type "list" expr)
+        (assert-equal "quasiquote" (symbol-name (first expr))))))
+
+  (deftest "unquote"
+    (let ((result (sx-parse ",foo")))
+      (assert-length 1 result)
+      (let ((expr (first result)))
+        (assert-type "list" expr)
+        (assert-equal "unquote" (symbol-name (first expr))))))
+
+  (deftest "splice-unquote"
+    (let ((result (sx-parse ",@foo")))
+      (assert-length 1 result)
+      (let ((expr (first result)))
+        (assert-type "list" expr)
+        (assert-equal "splice-unquote" (symbol-name (first expr)))))))
+
+
+;; --------------------------------------------------------------------------
+;; Serializer
+;; --------------------------------------------------------------------------
+
+(defsuite "serializer"
+  (deftest "serialize number"
+    (assert-equal "42" (sx-serialize 42)))
+
+  (deftest "serialize string"
+    (assert-equal "\"hello\"" (sx-serialize "hello")))
+
+  (deftest "serialize boolean"
+    (assert-equal "true" (sx-serialize true))
+    (assert-equal "false" (sx-serialize false)))
+
+  (deftest "serialize nil"
+    (assert-equal "nil" (sx-serialize nil)))
+
+  (deftest "serialize keyword"
+    (assert-equal ":foo" (sx-serialize (make-keyword "foo"))))
+
+  (deftest "serialize symbol"
+    (assert-equal "bar" (sx-serialize (make-symbol "bar"))))
+
+  (deftest "serialize list"
+    (assert-equal "(1 2 3)" (sx-serialize (list 1 2 3))))
+
+  (deftest "serialize empty list"
+    (assert-equal "()" (sx-serialize (list))))
+
+  (deftest "serialize nested"
+    (assert-equal "(1 (2 3) 4)" (sx-serialize (list 1 (list 2 3) 4)))))
+
+
+;; --------------------------------------------------------------------------
+;; Round-trip: parse then serialize
+;; --------------------------------------------------------------------------
+
+(defsuite "parser-roundtrip"
+  (deftest "roundtrip number"
+    (assert-equal "42" (sx-serialize (first (sx-parse "42")))))
+
+  (deftest "roundtrip string"
+    (assert-equal "\"hello\"" (sx-serialize (first (sx-parse "\"hello\"")))))
+
+  (deftest "roundtrip list"
+    (assert-equal "(1 2 3)" (sx-serialize (first (sx-parse "(1 2 3)")))))
+
+  (deftest "roundtrip nested"
+    (assert-equal "(a (b c))"
+      (sx-serialize (first (sx-parse "(a (b c))"))))))
diff --git a/shared/sx/ref/test-render.sx b/shared/sx/ref/test-render.sx
new file mode 100644
index 0000000..c714fc7
--- /dev/null
+++ b/shared/sx/ref/test-render.sx
@@ -0,0 +1,167 @@
+;; ==========================================================================
+;; test-render.sx — Tests for the HTML rendering adapter
+;;
+;; Requires: test-framework.sx loaded first.
+;; Modules tested: render.sx, adapter-html.sx
+;;
+;; Platform functions required (beyond test framework):
+;;   render-html   (sx-source)  -> HTML string
+;;     Parses the sx-source string, evaluates via render-to-html in a
+;;     fresh env, and returns the resulting HTML string.
+;;     (This is a test-only convenience that wraps parse + render-to-html.)
+;; ==========================================================================
+
+
+;; --------------------------------------------------------------------------
+;; Basic element rendering
+;; --------------------------------------------------------------------------
+
+(defsuite "render-elements"
+  (deftest "simple div"
+    (assert-equal "<div>hello</div>"
+      (render-html "(div \"hello\")")))
+
+  (deftest "nested elements"
+    (assert-equal "<div><span>hi</span></div>"
+      (render-html "(div (span \"hi\"))")))
+
+  (deftest "multiple children"
+    (assert-equal "<div><p>a</p><p>b</p></div>"
+      (render-html "(div (p \"a\") (p \"b\"))")))
+
+  (deftest "text content"
+    (assert-equal "<p>hello world</p>"
+      (render-html "(p \"hello\" \" world\")")))
+
+  (deftest "number content"
+    (assert-equal "<span>42</span>"
+      (render-html "(span 42)"))))
+
+
+;; --------------------------------------------------------------------------
+;; Attributes
+;; --------------------------------------------------------------------------
+
+(defsuite "render-attrs"
+  (deftest "string attribute"
+    (let ((html (render-html "(div :id \"main\" \"content\")")))
+      (assert-true (string-contains? html "id=\"main\""))
+      (assert-true (string-contains? html "content"))))
+
+  (deftest "class attribute"
+    (let ((html (render-html "(div :class \"foo bar\" \"x\")")))
+      (assert-true (string-contains? html "class=\"foo bar\""))))
+
+  (deftest "multiple attributes"
+    (let ((html (render-html "(a :href \"/home\" :class \"link\" \"Home\")")))
+      (assert-true (string-contains? html "href=\"/home\""))
+      (assert-true (string-contains? html "class=\"link\""))
+      (assert-true (string-contains? html "Home")))))
+
+
+;; --------------------------------------------------------------------------
+;; Void elements
+;; --------------------------------------------------------------------------
+
+(defsuite "render-void"
+  (deftest "br is self-closing"
+    (assert-equal "<br />" (render-html "(br)")))
+
+  (deftest "img with attrs"
+    (let ((html (render-html "(img :src \"pic.jpg\" :alt \"A pic\")")))
+      (assert-true (string-contains? html "<img"))
+      (assert-true (string-contains? html "src=\"pic.jpg\""))
+      (assert-true (string-contains? html "/>"))
+      ;; void elements should not have a closing tag
+      (assert-false (string-contains? html "</img>"))))
+
+  (deftest "input is self-closing"
+    (let ((html (render-html "(input :type \"text\" :name \"q\")")))
+      (assert-true (string-contains? html "<input"))
+      (assert-true (string-contains? html "/>")))))
+
+
+;; --------------------------------------------------------------------------
+;; Boolean attributes
+;; --------------------------------------------------------------------------
+
+(defsuite "render-boolean-attrs"
+  (deftest "true boolean attr emits name only"
+    (let ((html (render-html "(input :disabled true :type \"text\")")))
+      (assert-true (string-contains? html "disabled"))
+      ;; Should NOT have disabled="true"
+      (assert-false (string-contains? html "disabled=\""))))
+
+  (deftest "false boolean attr omitted"
+    (let ((html (render-html "(input :disabled false :type \"text\")")))
+      (assert-false (string-contains? html "disabled")))))
+
+
+;; --------------------------------------------------------------------------
+;; Fragments
+;; --------------------------------------------------------------------------
+
+(defsuite "render-fragments"
+  (deftest "fragment renders children without wrapper"
+    (assert-equal "<p>a</p><p>b</p>"
+      (render-html "(<> (p \"a\") (p \"b\"))")))
+
+  (deftest "empty fragment"
+    (assert-equal ""
+      (render-html "(<>)"))))
+
+
+;; --------------------------------------------------------------------------
+;; HTML escaping
+;; --------------------------------------------------------------------------
+
+(defsuite "render-escaping"
+  (deftest "text content is escaped"
+    (let ((html (render-html "(p \"<script>alert(1)</script>\")")))
+      (assert-false (string-contains? html "<script>"))
+      (assert-true (string-contains? html "&lt;script&gt;"))))
+
+  (deftest "attribute values are escaped"
+    (let ((html (render-html "(div :title \"a\\\"b\" \"x\")")))
+      (assert-true (string-contains? html "title=")))))
+
+
+;; --------------------------------------------------------------------------
+;; Control flow in render context
+;; --------------------------------------------------------------------------
+
+(defsuite "render-control-flow"
+  (deftest "if renders correct branch"
+    (assert-equal "<p>yes</p>"
+      (render-html "(if true (p \"yes\") (p \"no\"))"))
+    (assert-equal "<p>no</p>"
+      (render-html "(if false (p \"yes\") (p \"no\"))")))
+
+  (deftest "when renders or skips"
+    (assert-equal "<p>ok</p>"
+      (render-html "(when true (p \"ok\"))"))
+    (assert-equal ""
+      (render-html "(when false (p \"ok\"))")))
+
+  (deftest "map renders list"
+    (assert-equal "<li>1</li><li>2</li><li>3</li>"
+      (render-html "(map (fn (x) (li x)) (list 1 2 3))")))
+
+  (deftest "let in render context"
+    (assert-equal "<p>hello</p>"
+      (render-html "(let ((x \"hello\")) (p x))"))))
+
+
+;; --------------------------------------------------------------------------
+;; Component rendering
+;; --------------------------------------------------------------------------
+
+(defsuite "render-components"
+  (deftest "component with keyword args"
+    (assert-equal "<h1>Hello</h1>"
+      (render-html "(do (defcomp ~title (&key text) (h1 text)) (~title :text \"Hello\"))")))
+
+  (deftest "component with children"
+    (let ((html (render-html "(do (defcomp ~box (&key &rest children) (div :class \"box\" children)) (~box (p \"inside\")))")))
+      (assert-true (string-contains? html "class=\"box\""))
+      (assert-true (string-contains? html "<p>inside</p>")))))
diff --git a/shared/sx/ref/test-router.sx b/shared/sx/ref/test-router.sx
new file mode 100644
index 0000000..c84c2a3
--- /dev/null
+++ b/shared/sx/ref/test-router.sx
@@ -0,0 +1,125 @@
+;; ==========================================================================
+;; test-router.sx — Tests for client-side route matching
+;;
+;; Requires: test-framework.sx loaded first.
+;; Modules tested: router.sx
+;;
+;; No additional platform functions needed — router.sx is pure.
+;; ==========================================================================
+
+
+;; --------------------------------------------------------------------------
+;; split-path-segments
+;; --------------------------------------------------------------------------
+
+(defsuite "split-path-segments"
+  (deftest "root path"
+    (assert-equal (list) (split-path-segments "/")))
+
+  (deftest "single segment"
+    (assert-equal (list "docs") (split-path-segments "/docs")))
+
+  (deftest "multiple segments"
+    (assert-equal (list "docs" "hello") (split-path-segments "/docs/hello")))
+
+  (deftest "trailing slash stripped"
+    (assert-equal (list "docs") (split-path-segments "/docs/")))
+
+  (deftest "deep path"
+    (assert-equal (list "a" "b" "c" "d") (split-path-segments "/a/b/c/d"))))
+
+
+;; --------------------------------------------------------------------------
+;; parse-route-pattern
+;; --------------------------------------------------------------------------
+
+(defsuite "parse-route-pattern"
+  (deftest "static pattern"
+    (let ((segs (parse-route-pattern "/docs/intro")))
+      (assert-length 2 segs)
+      (assert-equal "literal" (get (first segs) "type"))
+      (assert-equal "docs" (get (first segs) "value"))
+      (assert-equal "literal" (get (nth segs 1) "type"))
+      (assert-equal "intro" (get (nth segs 1) "value"))))
+
+  (deftest "pattern with param"
+    (let ((segs (parse-route-pattern "/docs/<slug>")))
+      (assert-length 2 segs)
+      (assert-equal "literal" (get (first segs) "type"))
+      (assert-equal "docs" (get (first segs) "value"))
+      (assert-equal "param" (get (nth segs 1) "type"))
+      (assert-equal "slug" (get (nth segs 1) "value"))))
+
+  (deftest "multiple params"
+    (let ((segs (parse-route-pattern "/users/<uid>/posts/<pid>")))
+      (assert-length 4 segs)
+      (assert-equal "param" (get (nth segs 1) "type"))
+      (assert-equal "uid" (get (nth segs 1) "value"))
+      (assert-equal "param" (get (nth segs 3) "type"))
+      (assert-equal "pid" (get (nth segs 3) "value"))))
+
+  (deftest "root pattern"
+    (assert-equal (list) (parse-route-pattern "/"))))
+
+
+;; --------------------------------------------------------------------------
+;; match-route
+;; --------------------------------------------------------------------------
+
+(defsuite "match-route"
+  (deftest "exact match returns empty params"
+    (let ((result (match-route "/docs/intro" "/docs/intro")))
+      (assert-true (not (nil? result)))
+      (assert-length 0 (keys result))))
+
+  (deftest "param match extracts value"
+    (let ((result (match-route "/docs/hello" "/docs/<slug>")))
+      (assert-true (not (nil? result)))
+      (assert-equal "hello" (get result "slug"))))
+
+  (deftest "no match returns nil"
+    (assert-nil (match-route "/docs/hello" "/essays/<slug>"))
+    (assert-nil (match-route "/docs" "/docs/<slug>")))
+
+  (deftest "segment count mismatch returns nil"
+    (assert-nil (match-route "/a/b/c" "/a/<b>"))
+    (assert-nil (match-route "/a" "/a/b")))
+
+  (deftest "root matches root"
+    (let ((result (match-route "/" "/")))
+      (assert-true (not (nil? result)))))
+
+  (deftest "multiple params extracted"
+    (let ((result (match-route "/users/42/posts/99" "/users/<uid>/posts/<pid>")))
+      (assert-true (not (nil? result)))
+      (assert-equal "42" (get result "uid"))
+      (assert-equal "99" (get result "pid")))))
+
+
+;; --------------------------------------------------------------------------
+;; find-matching-route
+;; --------------------------------------------------------------------------
+
+(defsuite "find-matching-route"
+  (deftest "finds first matching route"
+    (let ((routes (list
+            {:pattern "/docs/" :parsed (parse-route-pattern "/docs/") :name "docs-index"}
+            {:pattern "/docs/<slug>" :parsed (parse-route-pattern "/docs/<slug>") :name "docs-page"})))
+      (let ((result (find-matching-route "/docs/hello" routes)))
+        (assert-true (not (nil? result)))
+        (assert-equal "docs-page" (get result "name"))
+        (assert-equal "hello" (get (get result "params") "slug")))))
+
+  (deftest "returns nil for no match"
+    (let ((routes (list
+            {:pattern "/docs/<slug>" :parsed (parse-route-pattern "/docs/<slug>") :name "docs-page"})))
+      (assert-nil (find-matching-route "/essays/hello" routes))))
+
+  (deftest "matches exact routes before param routes"
+    (let ((routes (list
+            {:pattern "/docs/" :parsed (parse-route-pattern "/docs/") :name "docs-index"}
+            {:pattern "/docs/<slug>" :parsed (parse-route-pattern "/docs/<slug>") :name "docs-page"})))
+      ;; /docs/ should match docs-index, not docs-page
+      (let ((result (find-matching-route "/docs/" routes)))
+        (assert-true (not (nil? result)))
+        (assert-equal "docs-index" (get result "name"))))))
diff --git a/shared/sx/ref/test.sx b/shared/sx/ref/test.sx
index 2f6fd97..30d7184 100644
--- a/shared/sx/ref/test.sx
+++ b/shared/sx/ref/test.sx
@@ -1,16 +1,21 @@
 ;; ==========================================================================
-;; test.sx — Self-hosting SX test framework
+;; test.sx — Self-hosting SX test suite (backward-compatible entry point)
 ;;
-;; Defines a minimal test framework in SX that tests SX — the language
-;; proves its own correctness. The framework is self-executing: any host
-;; that provides 5 platform functions can evaluate this file directly.
+;; This file includes the test framework and core eval tests inline.
+;; It exists for backward compatibility — runners that load "test.sx"
+;; get the same 81 tests as before.
+;;
+;; For modular testing, runners should instead load:
+;;   1. test-framework.sx  (macros + assertions)
+;;   2. One or more test specs: test-eval.sx, test-parser.sx,
+;;      test-router.sx, test-render.sx, etc.
 ;;
 ;; Platform functions required:
-;;   try-call     (thunk)        → {:ok true} | {:ok false :error "msg"}
-;;   report-pass  (name)         → platform-specific pass output
-;;   report-fail  (name error)   → platform-specific fail output
-;;   push-suite   (name)         → push suite name onto context stack
-;;   pop-suite    ()             → pop suite name from context stack
+;;   try-call     (thunk)        -> {:ok true} | {:ok false :error "msg"}
+;;   report-pass  (name)         -> platform-specific pass output
+;;   report-fail  (name error)   -> platform-specific fail output
+;;   push-suite   (name)         -> push suite name onto context stack
+;;   pop-suite    ()             -> pop suite name from context stack
 ;;
 ;; Usage:
 ;;   ;; Host injects platform functions into env, then:
diff --git a/shared/sx/tests/run.js b/shared/sx/tests/run.js
index ec77792..288f166 100644
--- a/shared/sx/tests/run.js
+++ b/shared/sx/tests/run.js
@@ -1,9 +1,13 @@
-// Run test.sx directly against sx-browser.js.
+// Run SX test specs against sx-browser.js.
 //
-// sx-browser.js parses and evaluates test.sx — SX tests itself.
+// sx-browser.js parses and evaluates test specs — SX tests itself.
 // This script provides only platform functions (error catching, reporting).
 //
-// Usage: node shared/sx/tests/run.js
+// Usage:
+//   node shared/sx/tests/run.js                     # run all available specs
+//   node shared/sx/tests/run.js eval                # run only test-eval.sx
+//   node shared/sx/tests/run.js eval parser router   # run specific specs
+//   node shared/sx/tests/run.js --legacy            # run monolithic test.sx
 
 Object.defineProperty(globalThis, "document", { value: undefined, writable: true });
 var path = require("path");
@@ -86,15 +90,149 @@ var env = {
   },
   "has-key?": function(d, k) { return d && typeof d === "object" && k in d; },
   "append": function(c, x) { return Array.isArray(x) ? (c||[]).concat(x) : (c||[]).concat([x]); },
+  "for-each-indexed": function(f, coll) {
+    for (var i = 0; i < (coll||[]).length; i++) {
+      Sx.eval([f, i, coll[i]], env);
+    }
+  },
+  "dict-set!": function(d, k, v) { if (d) d[k] = v; },
+  "dict-has?": function(d, k) { return d && typeof d === "object" && k in d; },
+  "dict-get": function(d, k) { return d ? d[k] : undefined; },
+  "starts-with?": function(s, prefix) { return String(s).indexOf(prefix) === 0; },
+  "ends-with?": function(s, suffix) { var str = String(s); return str.indexOf(suffix) === str.length - suffix.length; },
+  "slice": function(s, start, end) { return end !== undefined ? s.slice(start, end) : s.slice(start); },
+  "inc": function(n) { return n + 1; },
+  "append!": function(arr, item) { if (Array.isArray(arr)) arr.push(item); },
+  "dict": function() { return {}; },
+  "for-each": function(f, coll) {
+    for (var i = 0; i < (coll||[]).length; i++) {
+      Sx.eval([f, coll[i]], env);
+    }
+  },
+
+  // --- Parser platform functions (for test-parser.sx) ---
+  "sx-parse": function(source) { return Sx.parseAll(source); },
+  "sx-serialize": function(val) {
+    // Basic serializer for test roundtrips
+    if (val === Sx.NIL || val === null || val === undefined) return "nil";
+    if (typeof val === "boolean") return val ? "true" : "false";
+    if (typeof val === "number") return String(val);
+    if (typeof val === "string") return '"' + val.replace(/\\/g, "\\\\").replace(/"/g, '\\"') + '"';
+    // Check Symbol/Keyword BEFORE generic object — they are objects too
+    if (val && (val._sym || val._sx_symbol)) return val.name;
+    if (val && (val._kw || val._sx_keyword)) return ":" + val.name;
+    if (Array.isArray(val)) return "(" + val.map(function(x) { return env["sx-serialize"](x); }).join(" ") + ")";
+    if (val && typeof val === "object") {
+      var parts = [];
+      Object.keys(val).forEach(function(k) {
+        parts.push(":" + k);
+        parts.push(env["sx-serialize"](val[k]));
+      });
+      return "{" + parts.join(" ") + "}";
+    }
+    return String(val);
+  },
+  "make-symbol": function(name) { return Sx.sym ? Sx.sym(name) : { _sx_symbol: true, name: name, toString: function() { return name; } }; },
+  "make-keyword": function(name) { return Sx.kw ? Sx.kw(name) : { _sx_keyword: true, name: name, toString: function() { return name; } }; },
+  "symbol-name": function(s) { return s && s.name ? s.name : String(s); },
+  "keyword-name": function(k) { return k && k.name ? k.name : String(k); },
+
+  // --- Render platform function (for test-render.sx) ---
+  "render-html": function(sxSource) {
+    if (!Sx.renderToHtml) throw new Error("render-to-html not available — html adapter not bootstrapped");
+    var exprs = Sx.parseAll(sxSource);
+    var result = "";
+    for (var i = 0; i < exprs.length; i++) {
+      result += Sx.renderToHtml(exprs[i], env);
+    }
+    return result;
+  },
 };
 
-// --- Read and evaluate test.sx ---
-var src = fs.readFileSync(path.resolve(__dirname, "../ref/test.sx"), "utf8");
-var exprs = Sx.parseAll(src);
+// --- Resolve which test specs to run ---
+var refDir = path.resolve(__dirname, "../ref");
+var args = process.argv.slice(2);
 
-console.log("TAP version 13");
-for (var i = 0; i < exprs.length; i++) {
-  Sx.eval(exprs[i], env);
+// Available spec modules and their platform requirements
+var SPECS = {
+  "eval":    { file: "test-eval.sx",    needs: [] },
+  "parser":  { file: "test-parser.sx",  needs: ["sx-parse"] },
+  "router":  { file: "test-router.sx",  needs: [] },
+  "render":  { file: "test-render.sx",  needs: ["render-html"] },
+};
+
+function evalFile(filename) {
+  var filepath = path.resolve(refDir, filename);
+  if (!fs.existsSync(filepath)) {
+    console.log("# SKIP " + filename + " (file not found)");
+    return;
+  }
+  var src = fs.readFileSync(filepath, "utf8");
+  var exprs = Sx.parseAll(src);
+  for (var i = 0; i < exprs.length; i++) {
+    Sx.eval(exprs[i], env);
+  }
+}
+
+// Legacy mode — run monolithic test.sx
+if (args[0] === "--legacy") {
+  console.log("TAP version 13");
+  evalFile("test.sx");
+} else {
+  // Determine which specs to run
+  var specsToRun;
+  if (args.length > 0) {
+    specsToRun = args;
+  } else {
+    // Auto-discover: run all specs whose platform functions are available
+    specsToRun = Object.keys(SPECS);
+  }
+
+  console.log("TAP version 13");
+
+  // Always load framework first
+  evalFile("test-framework.sx");
+
+  // Load router.sx if testing router (it defines the functions being tested)
+  for (var si = 0; si < specsToRun.length; si++) {
+    var specName = specsToRun[si];
+    var spec = SPECS[specName];
+    if (!spec) {
+      console.log("# SKIP unknown spec: " + specName);
+      continue;
+    }
+
+    // Check platform requirements
+    var canRun = true;
+    for (var ni = 0; ni < spec.needs.length; ni++) {
+      if (!(spec.needs[ni] in env)) {
+        console.log("# SKIP " + specName + " (missing: " + spec.needs[ni] + ")");
+        canRun = false;
+        break;
+      }
+    }
+    if (!canRun) continue;
+
+    // Load prerequisite spec modules
+    if (specName === "router") {
+      // Use bootstrapped router functions from sx-browser.js.
+      // The bare evaluator can't run router.sx faithfully because set!
+      // inside lambda closures doesn't propagate (dict copies, not cells).
+      if (Sx.splitPathSegments) {
+        env["split-path-segments"] = Sx.splitPathSegments;
+        env["parse-route-pattern"] = Sx.parseRoutePattern;
+        env["match-route-segments"] = Sx.matchRouteSegments;
+        env["match-route"] = Sx.matchRoute;
+        env["find-matching-route"] = Sx.findMatchingRoute;
+        env["make-route-segment"] = Sx.makeRouteSegment;
+      } else {
+        evalFile("router.sx");
+      }
+    }
+
+    console.log("# --- " + specName + " ---");
+    evalFile(spec.file);
+  }
 }
 
 // --- Summary ---
diff --git a/shared/sx/tests/run.py b/shared/sx/tests/run.py
index 3fda836..eba2a03 100644
--- a/shared/sx/tests/run.py
+++ b/shared/sx/tests/run.py
@@ -1,23 +1,27 @@
 #!/usr/bin/env python3
-"""Run test.sx directly against the Python SX evaluator.
+"""Run SX test specs against the Python SX evaluator.
 
-The Python evaluator parses and evaluates test.sx — SX tests itself.
+The Python evaluator parses and evaluates test specs — SX tests itself.
 This script provides only platform functions (error catching, reporting).
 
-Usage: python shared/sx/tests/run.py
+Usage:
+    python shared/sx/tests/run.py                    # run all available specs
+    python shared/sx/tests/run.py eval               # run only test-eval.sx
+    python shared/sx/tests/run.py eval parser router  # run specific specs
+    python shared/sx/tests/run.py --legacy           # run monolithic test.sx
 """
 from __future__ import annotations
 
 import os
 import sys
-import traceback
 
 _HERE = os.path.dirname(os.path.abspath(__file__))
 _PROJECT = os.path.abspath(os.path.join(_HERE, "..", "..", ".."))
 sys.path.insert(0, _PROJECT)
 
 from shared.sx.parser import parse_all
-from shared.sx.evaluator import _eval, _trampoline
+from shared.sx.evaluator import _eval, _trampoline, _call_lambda
+from shared.sx.types import Symbol, Keyword, Lambda, NIL
 
 # --- Test state ---
 suite_stack: list[str] = []
@@ -29,7 +33,7 @@ test_num = 0
 def try_call(thunk):
     """Call an SX thunk, catching errors."""
     try:
-        _trampoline(_eval([thunk], {}))
+        _trampoline(_eval([thunk], env))
         return {"ok": True}
     except Exception as e:
         return {"ok": False, "error": str(e)}
@@ -60,25 +64,253 @@ def pop_suite():
     suite_stack.pop()
 
 
-def main():
-    env = {
-        "try-call": try_call,
-        "report-pass": report_pass,
-        "report-fail": report_fail,
-        "push-suite": push_suite,
-        "pop-suite": pop_suite,
-    }
+# --- Parser platform functions ---
 
-    test_sx = os.path.join(_HERE, "..", "ref", "test.sx")
-    with open(test_sx) as f:
+def sx_parse(source):
+    """Parse SX source string into list of AST expressions."""
+    return parse_all(source)
+
+
+def sx_serialize(val):
+    """Serialize an AST value to SX source text."""
+    if val is None or val is NIL:
+        return "nil"
+    if isinstance(val, bool):
+        return "true" if val else "false"
+    if isinstance(val, (int, float)):
+        return str(val)
+    if isinstance(val, str):
+        escaped = val.replace("\\", "\\\\").replace('"', '\\"')
+        return f'"{escaped}"'
+    if isinstance(val, Symbol):
+        return val.name
+    if isinstance(val, Keyword):
+        return f":{val.name}"
+    if isinstance(val, list):
+        inner = " ".join(sx_serialize(x) for x in val)
+        return f"({inner})"
+    if isinstance(val, dict):
+        parts = []
+        for k, v in val.items():
+            parts.append(f":{k}")
+            parts.append(sx_serialize(v))
+        return "{" + " ".join(parts) + "}"
+    return str(val)
+
+
+def make_symbol(name):
+    return Symbol(name)
+
+
+def make_keyword(name):
+    return Keyword(name)
+
+
+def symbol_name(sym):
+    if isinstance(sym, Symbol):
+        return sym.name
+    return str(sym)
+
+
+def keyword_name(kw):
+    if isinstance(kw, Keyword):
+        return kw.name
+    return str(kw)
+
+
+# --- Render platform function ---
+
+def render_html(sx_source):
+    """Parse SX source and render to HTML via the bootstrapped evaluator."""
+    try:
+        from shared.sx.ref.sx_ref import render_to_html as _render_to_html
+    except ImportError:
+        raise RuntimeError("render-to-html not available — sx_ref.py not built")
+    exprs = parse_all(sx_source)
+    render_env = dict(env)
+    result = ""
+    for expr in exprs:
+        result += _render_to_html(expr, render_env)
+    return result
+
+
+# --- Spec registry ---
+
+SPECS = {
+    "eval":   {"file": "test-eval.sx",   "needs": []},
+    "parser": {"file": "test-parser.sx", "needs": ["sx-parse"]},
+    "router": {"file": "test-router.sx", "needs": []},
+    "render": {"file": "test-render.sx", "needs": ["render-html"]},
+}
+
+REF_DIR = os.path.join(_HERE, "..", "ref")
+
+
+def eval_file(filename, env):
+    """Load and evaluate an SX file."""
+    filepath = os.path.join(REF_DIR, filename)
+    if not os.path.exists(filepath):
+        print(f"# SKIP {filename} (file not found)")
+        return
+    with open(filepath) as f:
         src = f.read()
-
     exprs = parse_all(src)
-
-    print("TAP version 13")
     for expr in exprs:
         _trampoline(_eval(expr, env))
 
+
+# --- Build env ---
+env = {
+    "try-call": try_call,
+    "report-pass": report_pass,
+    "report-fail": report_fail,
+    "push-suite": push_suite,
+    "pop-suite": pop_suite,
+    # Parser platform functions
+    "sx-parse": sx_parse,
+    "sx-serialize": sx_serialize,
+    "make-symbol": make_symbol,
+    "make-keyword": make_keyword,
+    "symbol-name": symbol_name,
+    "keyword-name": keyword_name,
+    # Render platform function
+    "render-html": render_html,
+    # Extra primitives needed by spec modules (router.sx, deps.sx)
+    "for-each-indexed": "_deferred",  # replaced below
+    "dict-set!": "_deferred",
+    "dict-has?": "_deferred",
+    "dict-get": "_deferred",
+    "append!": "_deferred",
+    "inc": lambda n: n + 1,
+}
+
+
+def _call_sx(fn, args, caller_env):
+    """Call an SX lambda or native function with args."""
+    if isinstance(fn, Lambda):
+        return _trampoline(_call_lambda(fn, list(args), caller_env))
+    return fn(*args)
+
+
+def _for_each_indexed(fn, coll):
+    """for-each-indexed that respects set! in lambda closures.
+
+    The hand-written evaluator copies envs on lambda calls, which breaks
+    set! mutation of outer scope. We eval directly in the closure dict
+    to match the bootstrapped semantics (cell-based mutation).
+    """
+    if isinstance(fn, Lambda):
+        closure = fn.closure
+        for i, item in enumerate(coll or []):
+            # Bind params directly in the closure (no copy)
+            for p, v in zip(fn.params, [i, item]):
+                closure[p] = v
+            _trampoline(_eval(fn.body, closure))
+    else:
+        for i, item in enumerate(coll or []):
+            fn(i, item)
+    return NIL
+
+
+def _dict_set(d, k, v):
+    if isinstance(d, dict):
+        d[k] = v
+    return NIL
+
+
+def _dict_has(d, k):
+    return isinstance(d, dict) and k in d
+
+
+def _dict_get(d, k):
+    if isinstance(d, dict):
+        return d.get(k, NIL)
+    return NIL
+
+
+def _append_mut(lst, item):
+    if isinstance(lst, list):
+        lst.append(item)
+    return NIL
+
+
+env["for-each-indexed"] = _for_each_indexed
+env["dict-set!"] = _dict_set
+env["dict-has?"] = _dict_has
+env["dict-get"] = _dict_get
+env["append!"] = _append_mut
+
+
+def _load_router_from_bootstrap(env):
+    """Load router functions from the bootstrapped sx_ref.py.
+
+    The hand-written evaluator can't run router.sx faithfully because
+    set! inside lambda closures doesn't propagate to outer scopes
+    (the evaluator uses dict copies, not cells). The bootstrapped code
+    compiles set! to cell-based mutation, so we import from there.
+    """
+    try:
+        from shared.sx.ref.sx_ref import (
+            split_path_segments,
+            parse_route_pattern,
+            match_route_segments,
+            match_route,
+            find_matching_route,
+            make_route_segment,
+        )
+        env["split-path-segments"] = split_path_segments
+        env["parse-route-pattern"] = parse_route_pattern
+        env["match-route-segments"] = match_route_segments
+        env["match-route"] = match_route
+        env["find-matching-route"] = find_matching_route
+        env["make-route-segment"] = make_route_segment
+    except ImportError:
+        # Fallback: eval router.sx directly (may fail on set! scoping)
+        eval_file("router.sx", env)
+
+
+def main():
+    global passed, failed, test_num
+
+    args = sys.argv[1:]
+
+    # Legacy mode
+    if args and args[0] == "--legacy":
+        print("TAP version 13")
+        eval_file("test.sx", env)
+    else:
+        # Determine which specs to run
+        specs_to_run = args if args else list(SPECS.keys())
+
+        print("TAP version 13")
+
+        # Always load framework first
+        eval_file("test-framework.sx", env)
+
+        for spec_name in specs_to_run:
+            spec = SPECS.get(spec_name)
+            if not spec:
+                print(f"# SKIP unknown spec: {spec_name}")
+                continue
+
+            # Check platform requirements
+            can_run = True
+            for need in spec["needs"]:
+                if need not in env:
+                    print(f"# SKIP {spec_name} (missing: {need})")
+                    can_run = False
+                    break
+            if not can_run:
+                continue
+
+            # Load prerequisite spec modules
+            if spec_name == "router":
+                _load_router_from_bootstrap(env)
+
+            print(f"# --- {spec_name} ---")
+            eval_file(spec["file"], env)
+
+    # Summary
     print()
     print(f"1..{test_num}")
     print(f"# tests {passed + failed}")
diff --git a/sx/sx/boundary.sx b/sx/sx/boundary.sx
index 87d062b..fb5dd2a 100644
--- a/sx/sx/boundary.sx
+++ b/sx/sx/boundary.sx
@@ -64,3 +64,8 @@
   :params ()
   :returns "dict"
   :service "sx")
+
+(define-page-helper "run-modular-tests"
+  :params (spec-name)
+  :returns "dict"
+  :service "sx")
diff --git a/sx/sx/layouts.sx b/sx/sx/layouts.sx
index 817f450..32f085b 100644
--- a/sx/sx/layouts.sx
+++ b/sx/sx/layouts.sx
@@ -14,6 +14,7 @@
            (dict :label "Essays" :href "/essays/")
            (dict :label "Specs" :href "/specs/")
            (dict :label "Bootstrappers" :href "/bootstrappers/")
+           (dict :label "Testing" :href "/testing/")
            (dict :label "Isomorphism" :href "/isomorphism/")
            (dict :label "Plans" :href "/plans/"))))
     (<> (map (lambda (item)
diff --git a/sx/sx/nav-data.sx b/sx/sx/nav-data.sx
index b534a96..03a560e 100644
--- a/sx/sx/nav-data.sx
+++ b/sx/sx/nav-data.sx
@@ -107,8 +107,15 @@
   (dict :label "Continuations" :href "/specs/continuations")
   (dict :label "call/cc" :href "/specs/callcc")
   (dict :label "Deps" :href "/specs/deps")
-  (dict :label "Router" :href "/specs/router")
-  (dict :label "Testing" :href "/specs/testing")))
+  (dict :label "Router" :href "/specs/router")))
+
+(define testing-nav-items (list
+  (dict :label "Overview" :href "/testing/")
+  (dict :label "Evaluator" :href "/testing/eval")
+  (dict :label "Parser" :href "/testing/parser")
+  (dict :label "Router" :href "/testing/router")
+  (dict :label "Renderer" :href "/testing/render")
+  (dict :label "Runners" :href "/testing/runners")))
 
 (define isomorphism-nav-items (list
   (dict :label "Roadmap" :href "/isomorphism/")
@@ -201,10 +208,7 @@
         :prose "The deps module analyzes component dependency graphs and classifies components as pure or IO-dependent. Phase 1 (bundling): walks component AST bodies to find transitive ~component references, computes the minimal set needed per page, and collects per-page CSS classes from only the used components. Phase 2 (IO detection): scans component ASTs for references to IO primitive names (from boundary.sx declarations — frag, query, service, current-user, highlight, etc.), computes transitive IO refs through the component graph, and caches the result on each component. Components with no transitive IO refs are pure — they can render anywhere without server data. IO-dependent components must expand server-side. The spec provides the classification; each host's async partial evaluator acts on it (expand IO-dependent server-side, serialize pure for client). All functions are pure — each host bootstraps them to native code via --spec-modules deps. Platform functions (component-deps, component-set-deps!, component-css-classes, component-io-refs, component-set-io-refs!, env-components, regex-find-all, scan-css-classes) are implemented natively per target.")
   (dict :slug "router" :filename "router.sx" :title "Router"
         :desc "Client-side route matching — Flask-style pattern parsing, segment matching, route table search."
-        :prose "The router module provides pure functions for matching URL paths against Flask-style route patterns (e.g. /docs/<slug>). Used by client-side routing (Phase 3) to determine if a page can be rendered locally without a server roundtrip. split-path-segments breaks a path into segments, parse-route-pattern converts patterns into typed segment descriptors, match-route-segments tests a path against a parsed pattern returning extracted params, and find-matching-route searches a route table for the first match. No platform interface needed — uses only pure string and list primitives. Bootstrapped via --spec-modules deps,router.")
-  (dict :slug "testing" :filename "test.sx" :title "Testing"
-        :desc "Self-hosting test framework — SX tests SX. Bootstraps to pytest and Node.js TAP."
-        :prose "The test spec defines a minimal test framework in SX that bootstraps to every host. Tests are written in SX and verify SX semantics — the language tests itself. The framework uses only primitives already in primitives.sx (assert, equal?, type-of, str, list, len) plus assertion helpers defined in SX (assert-equal, assert-true, assert-false, assert-nil, assert-type, assert-length, assert-contains). Two bootstrap compilers read test.sx and emit native test files: bootstrap_test.py produces a pytest module, bootstrap_test_js.py produces a Node.js TAP script. The same 81 tests run on both platforms, verifying cross-host parity.")))
+        :prose "The router module provides pure functions for matching URL paths against Flask-style route patterns (e.g. /docs/<slug>). Used by client-side routing (Phase 3) to determine if a page can be rendered locally without a server roundtrip. split-path-segments breaks a path into segments, parse-route-pattern converts patterns into typed segment descriptors, match-route-segments tests a path against a parsed pattern returning extracted params, and find-matching-route searches a route table for the first match. No platform interface needed — uses only pure string and list primitives. Bootstrapped via --spec-modules deps,router.")))
 
 (define all-spec-items (concat core-spec-items (concat adapter-spec-items (concat browser-spec-items (concat extension-spec-items module-spec-items)))))
 
diff --git a/sx/sx/testing.sx b/sx/sx/testing.sx
index 6c4ab4a..6bb96e6 100644
--- a/sx/sx/testing.sx
+++ b/sx/sx/testing.sx
@@ -1,246 +1,288 @@
-;; Testing spec page — SX tests SX.
+;; Testing section — SX tests SX across every host.
+;; Modular test specs: eval, parser, router, render.
+;; Each page shows spec source, runs server-side, offers browser-side run button.
 
-(defcomp ~spec-testing-content (&key spec-source server-results)
+;; ---------------------------------------------------------------------------
+;; Overview page
+;; ---------------------------------------------------------------------------
+
+(defcomp ~testing-overview-content (&key server-results framework-source eval-source parser-source router-source render-source)
   (~doc-page :title "Testing"
     (div :class "space-y-8"
 
       ;; Intro
       (div :class "space-y-4"
         (p :class "text-lg text-stone-600"
-          "SX tests itself. "
-          (code :class "text-violet-700 text-sm" "test.sx")
-          " is a self-executing test spec — it defines "
+          "SX tests itself. Test specs are written in SX and executed by SX evaluators on every host. "
+          "The same assertions run in Python, Node.js, and in the browser — from the same source files.")
+        (p :class "text-stone-600"
+          "The framework defines two macros ("
           (code :class "text-violet-700 text-sm" "deftest")
           " and "
           (code :class "text-violet-700 text-sm" "defsuite")
-          " as macros, writes 81 test cases, and runs them. Any host that provides five platform functions can evaluate the file directly.")
-        (p :class "text-stone-600"
-          "This is not a test "
-          (em "of") " SX — it is a test " (em "in") " SX. The same s-expressions that define how "
-          (code :class "text-violet-700 text-sm" "if")
-          " works are used to verify that "
-          (code :class "text-violet-700 text-sm" "if")
-          " works. No code generation, no intermediate files — the evaluator runs the spec."))
+          ") and nine assertion helpers, all in SX. Each host provides only "
+          (strong "five platform functions")
+          " — everything else is pure SX."))
 
-      ;; Server-side results (ran when this page was rendered)
-      (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "Server: Python evaluator")
-        (p :class "text-stone-600"
-          "The Python evaluator ran "
-          (code :class "text-violet-700 text-sm" "test.sx")
-          " when this page loaded — "
-          (strong (str (get server-results "passed") "/" (get server-results "total") " passed"))
-          " in " (str (get server-results "elapsed-ms")) "ms.")
-        (pre :class "text-sm font-mono bg-stone-900 text-green-400 rounded-lg p-4 overflow-x-auto max-h-96 overflow-y-auto"
-          (get server-results "output")))
-
-      ;; Client-side test runner
-      (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "Browser: JavaScript evaluator")
-        (p :class "text-stone-600"
-          "This page loaded "
-          (code :class "text-violet-700 text-sm" "sx-browser.js")
-          " to render itself. The same evaluator can run "
-          (code :class "text-violet-700 text-sm" "test.sx")
-          " right here:")
-        (div :class "flex items-center gap-4"
-          (button :id "test-btn"
-            :class "px-4 py-2 rounded-md bg-violet-600 text-white font-medium text-sm hover:bg-violet-700 cursor-pointer"
-            :onclick "sxRunTests('test-sx-source','test-output','test-btn')"
-            "Run 81 tests"))
-        (pre :id "test-output"
-          :class "text-sm font-mono bg-stone-900 text-green-400 rounded-lg p-4 overflow-x-auto max-h-96 overflow-y-auto"
-          :style "display:none"
-          "")
-        ;; Hidden: raw test.sx source for the browser runner
-        (textarea :id "test-sx-source" :style "display:none" spec-source)
-        ;; Load the test runner script
-        (script :src (asset-url "/scripts/sx-test-runner.js")))
-
-      ;; How it works
+      ;; Architecture
       (div :class "space-y-3"
         (h2 :class "text-2xl font-semibold text-stone-800" "Architecture")
-        (p :class "text-stone-600"
-          "The test framework needs five platform functions. Everything else — macros, assertion helpers, test suites — is pure SX:")
         (div :class "not-prose bg-stone-100 rounded-lg p-5 mx-auto max-w-3xl"
           (pre :class "text-sm leading-relaxed whitespace-pre-wrap break-words font-mono text-stone-700"
-"test.sx                       Self-executing: macros + helpers + 81 tests
+"test-framework.sx            Macros + assertion helpers (loaded first)
     |
-    |--- browser                sx-browser.js evaluates test.sx in this page
-    |
-    |--- run.js                 Injects 5 platform fns, evaluates test.sx
-    |       |
-    |       +-> sx-browser.js   JS evaluator (bootstrapped from spec)
-    |
-    |--- run.py                 Injects 5 platform fns, evaluates test.sx
-            |
-            +-> evaluator.py    Python evaluator
+    +-- test-eval.sx           81 tests: evaluator + primitives
+    +-- test-parser.sx         39 tests: tokenizer, parser, serializer
+    +-- test-router.sx         18 tests: route matching + param extraction
+    +-- test-render.sx         23 tests: HTML rendering + components
 
-Platform functions (5 total — everything else is pure SX):
+Runners:
+    run.js                     Node.js — injects platform fns, runs specs
+    run.py                     Python — injects platform fns, runs specs
+    sx-test-runner.js          Browser — runs specs in this page
+
+Platform functions (5 total):
     try-call (thunk)          -> {:ok true} | {:ok false :error \"msg\"}
     report-pass (name)        -> output pass
     report-fail (name error)  -> output fail
     push-suite (name)         -> push suite context
-    pop-suite ()              -> pop suite context")))
+    pop-suite ()              -> pop suite context
 
-      ;; Framework
-      (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "The test framework")
-        (p :class "text-stone-600"
-          "The framework defines two macros and nine assertion helpers, all in SX. The macros are the key — they make "
-          (code :class "text-violet-700 text-sm" "defsuite")
-          " and "
-          (code :class "text-violet-700 text-sm" "deftest")
-          " executable forms, not just declarations:")
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "Macros")
-          (~doc-code :code
-            (highlight "(defmacro deftest (name &rest body)\n  `(let ((result (try-call (fn () ,@body))))\n     (if (get result \"ok\")\n       (report-pass ,name)\n       (report-fail ,name (get result \"error\")))))\n\n(defmacro defsuite (name &rest items)\n  `(do (push-suite ,name)\n       ,@items\n       (pop-suite)))" "lisp")))
-        (p :class "text-stone-600 text-sm"
-          (code :class "text-violet-700 text-sm" "deftest")
-          " wraps the body in a thunk, passes it to "
-          (code :class "text-violet-700 text-sm" "try-call")
-          " (the one platform function that catches errors), then reports pass or fail. "
-          (code :class "text-violet-700 text-sm" "defsuite")
-          " pushes a name onto the context stack, runs its children, and pops.")
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "Assertion helpers")
-          (~doc-code :code
-            (highlight "(define assert-equal\n  (fn (expected actual)\n    (assert (equal? expected actual)\n      (str \"Expected \" (str expected) \" but got \" (str actual)))))\n\n(define assert-true  (fn (val) (assert val ...)))\n(define assert-false (fn (val) (assert (not val) ...)))\n(define assert-nil   (fn (val) (assert (nil? val) ...)))\n(define assert-type  (fn (expected-type val) ...))\n(define assert-length (fn (expected-len col) ...))\n(define assert-contains (fn (item col) ...))\n(define assert-throws (fn (thunk) ...))" "lisp"))))
+Per-spec platform functions:
+    parser:  sx-parse, sx-serialize, make-symbol, make-keyword, ...
+    router:  (none — pure spec, uses bootstrapped functions)
+    render:  render-html (wraps parse + render-to-html)")))
 
-      ;; Example tests
-      (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "Example: SX testing SX")
-        (p :class "text-stone-600"
-          "The test suites cover every language feature. Here is the arithmetic suite testing the evaluator's arithmetic primitives:")
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "From test.sx")
-          (~doc-code :code
-            (highlight "(defsuite \"arithmetic\"\n  (deftest \"addition\"\n    (assert-equal 3 (+ 1 2))\n    (assert-equal 0 (+ 0 0))\n    (assert-equal -1 (+ 1 -2))\n    (assert-equal 10 (+ 1 2 3 4)))\n\n  (deftest \"subtraction\"\n    (assert-equal 1 (- 3 2))\n    (assert-equal -1 (- 2 3)))\n\n  (deftest \"multiplication\"\n    (assert-equal 6 (* 2 3))\n    (assert-equal 0 (* 0 100))\n    (assert-equal 24 (* 1 2 3 4)))\n\n  (deftest \"division\"\n    (assert-equal 2 (/ 6 3))\n    (assert-equal 2.5 (/ 5 2)))\n\n  (deftest \"modulo\"\n    (assert-equal 1 (mod 7 3))\n    (assert-equal 0 (mod 6 3))))" "lisp"))))
+      ;; Server results
+      (when server-results
+        (div :class "space-y-3"
+          (h2 :class "text-2xl font-semibold text-stone-800" "Server: Python evaluator")
+          (p :class "text-stone-600"
+            "Ran all test specs when this page loaded — "
+            (strong (str (get server-results "passed") "/" (get server-results "total") " passed"))
+            " in " (str (get server-results "elapsed-ms")) "ms.")
+          (pre :class "text-sm font-mono bg-stone-900 text-green-400 rounded-lg p-4 overflow-x-auto max-h-96 overflow-y-auto"
+            (get server-results "output"))))
 
-      ;; Running tests — JS
+      ;; Browser test runner
       (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "JavaScript: direct evaluation")
+        (h2 :class "text-2xl font-semibold text-stone-800" "Browser: JavaScript evaluator")
         (p :class "text-stone-600"
+          "Run all test specs in the browser using "
           (code :class "text-violet-700 text-sm" "sx-browser.js")
-          " evaluates "
-          (code :class "text-violet-700 text-sm" "test.sx")
-          " directly. The runner injects platform functions and calls "
-          (code :class "text-violet-700 text-sm" "Sx.eval")
-          " on each parsed expression:")
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "run.js")
-          (~doc-code :code
-            (highlight "var Sx = require('./sx-browser.js');\nvar src = fs.readFileSync('test.sx', 'utf8');\n\nvar env = {\n  'try-call': function(thunk) {\n    try {\n      Sx.eval([thunk], env);   // call the SX lambda\n      return { ok: true };\n    } catch(e) {\n      return { ok: false, error: e.message };\n    }\n  },\n  'report-pass': function(name) { console.log('ok - ' + name); },\n  'report-fail': function(name, err) { console.log('not ok - ' + name); },\n  'push-suite': function(n) { stack.push(n); },\n  'pop-suite':  function()  { stack.pop(); },\n};\n\nvar exprs = Sx.parseAll(src);\nfor (var i = 0; i < exprs.length; i++) Sx.eval(exprs[i], env);" "javascript")))
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "Output")
-          (~doc-code :code
-            (highlight "$ node shared/sx/tests/run.js\nTAP version 13\nok 1 - literals > numbers are numbers\nok 2 - literals > strings are strings\n...\nok 81 - edge-cases > empty operations\n\n# tests 81\n# pass  81" "bash"))))
+          ":")
+        (div :class "flex items-center gap-4"
+          (button :id "test-btn-all"
+            :class "px-4 py-2 rounded-md bg-violet-600 text-white font-medium text-sm hover:bg-violet-700 cursor-pointer"
+            :onclick "sxRunModularTests('all','test-output-all','test-btn-all')"
+            "Run all tests"))
+        (pre :id "test-output-all"
+          :class "text-sm font-mono bg-stone-900 text-green-400 rounded-lg p-4 overflow-x-auto max-h-96 overflow-y-auto"
+          :style "display:none"
+          "")
+        ;; Hidden: all spec sources for the browser runner
+        (textarea :id "test-framework-source" :style "display:none" framework-source)
+        (textarea :id "test-spec-eval" :style "display:none" eval-source)
+        (textarea :id "test-spec-parser" :style "display:none" parser-source)
+        (textarea :id "test-spec-router" :style "display:none" router-source)
+        (textarea :id "test-spec-render" :style "display:none" render-source)
+        (script :src (asset-url "/scripts/sx-test-runner.js")))
 
-      ;; Running tests — Python
+      ;; Test spec index
       (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "Python: direct evaluation")
-        (p :class "text-stone-600"
-          "Same approach — the Python evaluator runs "
-          (code :class "text-violet-700 text-sm" "test.sx")
-          " directly:")
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "run.py")
-          (~doc-code :code
-            (highlight "from shared.sx.parser import parse_all\nfrom shared.sx.evaluator import _eval, _trampoline\n\ndef try_call(thunk):\n    try:\n        _trampoline(_eval([thunk], {}))\n        return {'ok': True}\n    except Exception as e:\n        return {'ok': False, 'error': str(e)}\n\nenv = {\n    'try-call': try_call,\n    'report-pass': report_pass,\n    'report-fail': report_fail,\n    'push-suite': push_suite,\n    'pop-suite': pop_suite,\n}\n\nfor expr in parse_all(src):\n    _trampoline(_eval(expr, env))" "python")))
-        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
-          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "Output")
-          (~doc-code :code
-            (highlight "$ python shared/sx/tests/run.py\nTAP version 13\nok 1 - literals > numbers are numbers\n...\nok 81 - edge-cases > empty operations\n\n# tests 81\n# pass  81" "bash"))))
+        (h2 :class "text-2xl font-semibold text-stone-800" "Test specs")
+        (div :class "grid grid-cols-1 md:grid-cols-2 gap-4"
+          (a :href "/testing/eval" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
+            (h3 :class "font-semibold text-stone-800" "Evaluator")
+            (p :class "text-sm text-stone-500" "81 tests — literals, arithmetic, strings, lists, dicts, special forms, lambdas, components, macros")
+            (p :class "text-xs text-violet-600 mt-1" "test-eval.sx"))
+          (a :href "/testing/parser" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
+            (h3 :class "font-semibold text-stone-800" "Parser")
+            (p :class "text-sm text-stone-500" "39 tests — tokenization, parsing, escape sequences, quote sugar, serialization, round-trips")
+            (p :class "text-xs text-violet-600 mt-1" "test-parser.sx"))
+          (a :href "/testing/router" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
+            (h3 :class "font-semibold text-stone-800" "Router")
+            (p :class "text-sm text-stone-500" "18 tests — path splitting, pattern parsing, segment matching, parameter extraction")
+            (p :class "text-xs text-violet-600 mt-1" "test-router.sx"))
+          (a :href "/testing/render" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
+            (h3 :class "font-semibold text-stone-800" "Renderer")
+            (p :class "text-sm text-stone-500" "23 tests — elements, attributes, void elements, fragments, escaping, control flow, components")
+            (p :class "text-xs text-violet-600 mt-1" "test-render.sx"))))
 
       ;; What it proves
       (div :class "rounded-lg border border-blue-200 bg-blue-50 p-5 space-y-3"
         (h2 :class "text-lg font-semibold text-blue-900" "What this proves")
         (ol :class "list-decimal list-inside text-blue-800 space-y-2 text-sm"
-          (li "The test spec is " (strong "written in SX") " and " (strong "executed by SX") " — no code generation")
-          (li "The same 81 tests run on " (strong "Python, Node.js, and in the browser") " from the same file")
+          (li "Test specs are " (strong "written in SX") " and " (strong "executed by SX") " — no code generation")
+          (li "The same tests run on " (strong "Python, Node.js, and in the browser") " from the same files")
           (li "Each host provides only " (strong "5 platform functions") " — everything else is pure SX")
-          (li "Adding a new host means implementing 5 functions, not rewriting tests")
-          (li "Platform divergences (truthiness of 0, [], \"\") are " (strong "documented, not hidden"))
-          (li "The spec is " (strong "executable") " — click the button above to prove it")))
+          (li "Modular specs test each part independently — evaluator, parser, router, renderer")
+          (li "Per-spec platform functions extend the 5-function contract for module-specific capabilities")
+          (li "Platform divergences are " (strong "exposed by the tests") ", not hidden"))))))
 
-      ;; Test suites
+
+;; ---------------------------------------------------------------------------
+;; Per-spec test page (reusable for eval, parser, router, render)
+;; ---------------------------------------------------------------------------
+
+(defcomp ~testing-spec-content (&key spec-name spec-title spec-desc spec-source framework-source server-results)
+  (~doc-page :title spec-title
+    (div :class "space-y-8"
+
+      ;; Description
+      (div :class "space-y-4"
+        (p :class "text-lg text-stone-600" spec-desc))
+
+      ;; Server-side results
+      (when server-results
+        (div :class "space-y-3"
+          (h2 :class "text-2xl font-semibold text-stone-800" "Server: Python evaluator")
+          (p :class "text-stone-600"
+            "Ran "
+            (code :class "text-violet-700 text-sm" (str "test-" spec-name ".sx"))
+            " when this page loaded — "
+            (strong (str (get server-results "passed") "/" (get server-results "total") " passed"))
+            " in " (str (get server-results "elapsed-ms")) "ms.")
+          (pre :class "text-sm font-mono bg-stone-900 text-green-400 rounded-lg p-4 overflow-x-auto max-h-96 overflow-y-auto"
+            (get server-results "output"))))
+
+      ;; Browser test runner
       (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "All 15 test suites")
-        (div :class "overflow-x-auto rounded border border-stone-200"
-          (table :class "w-full text-left text-sm"
-            (thead (tr :class "border-b border-stone-200 bg-stone-100"
-              (th :class "px-3 py-2 font-medium text-stone-600" "Suite")
-              (th :class "px-3 py-2 font-medium text-stone-600" "Tests")
-              (th :class "px-3 py-2 font-medium text-stone-600" "Covers")))
-            (tbody
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "literals")
-                (td :class "px-3 py-2" "6")
-                (td :class "px-3 py-2 text-stone-700" "number, string, boolean, nil, list, dict type checking"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "arithmetic")
-                (td :class "px-3 py-2" "5")
-                (td :class "px-3 py-2 text-stone-700" "+, -, *, /, mod with edge cases"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "comparison")
-                (td :class "px-3 py-2" "3")
-                (td :class "px-3 py-2 text-stone-700" "=, equal?, <, >, <=, >="))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "strings")
-                (td :class "px-3 py-2" "7")
-                (td :class "px-3 py-2 text-stone-700" "str, string-length, substring, contains?, upcase, trim, split/join"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "lists")
-                (td :class "px-3 py-2" "10")
-                (td :class "px-3 py-2 text-stone-700" "first, rest, nth, last, cons, append, reverse, empty?, contains?, flatten"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "dicts")
-                (td :class "px-3 py-2" "6")
-                (td :class "px-3 py-2 text-stone-700" "literals, get, assoc, dissoc, keys/vals, has-key?, merge"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "predicates")
-                (td :class "px-3 py-2" "7")
-                (td :class "px-3 py-2 text-stone-700" "nil?, number?, string?, list?, dict?, boolean?, not"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "special-forms")
-                (td :class "px-3 py-2" "10")
-                (td :class "px-3 py-2 text-stone-700" "if, when, cond, and, or, let, let (Clojure), do/begin, define, set!"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "lambdas")
-                (td :class "px-3 py-2" "5")
-                (td :class "px-3 py-2 text-stone-700" "basic, closures, as argument, recursion, higher-order returns"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "higher-order")
-                (td :class "px-3 py-2" "6")
-                (td :class "px-3 py-2 text-stone-700" "map, filter, reduce, some, every?, map-indexed"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "components")
-                (td :class "px-3 py-2" "4")
-                (td :class "px-3 py-2 text-stone-700" "defcomp, &key params, &rest children, defaults"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "macros")
-                (td :class "px-3 py-2" "3")
-                (td :class "px-3 py-2 text-stone-700" "defmacro, quasiquote/unquote, splice-unquote"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "threading")
-                (td :class "px-3 py-2" "1")
-                (td :class "px-3 py-2 text-stone-700" "-> thread-first macro"))
-              (tr :class "border-b border-stone-100"
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "truthiness")
-                (td :class "px-3 py-2" "2")
-                (td :class "px-3 py-2 text-stone-700" "truthy/falsy values (platform-universal subset)"))
-              (tr
-                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "edge-cases")
-                (td :class "px-3 py-2" "6")
-                (td :class "px-3 py-2 text-stone-700" "nested scoping, recursive map, keywords, dict eval, nil propagation, empty ops"))))))
+        (h2 :class "text-2xl font-semibold text-stone-800" "Browser: JavaScript evaluator")
+        (p :class "text-stone-600"
+          "Run this spec in the browser:")
+        (div :class "flex items-center gap-4"
+          (button :id (str "test-btn-" spec-name)
+            :class "px-4 py-2 rounded-md bg-violet-600 text-white font-medium text-sm hover:bg-violet-700 cursor-pointer"
+            :onclick (str "sxRunModularTests('" spec-name "','test-output-" spec-name "','test-btn-" spec-name "')")
+            (str "Run " spec-title)))
+        (pre :id (str "test-output-" spec-name)
+          :class "text-sm font-mono bg-stone-900 text-green-400 rounded-lg p-4 overflow-x-auto max-h-96 overflow-y-auto"
+          :style "display:none"
+          "")
+        ;; Hidden: spec source + framework source for the browser runner
+        (textarea :id (str "test-spec-" spec-name) :style "display:none" spec-source)
+        (textarea :id "test-framework-source" :style "display:none" framework-source)
+        (script :src (asset-url "/scripts/sx-test-runner.js")))
 
       ;; Full source
       (div :class "space-y-3"
-        (h2 :class "text-2xl font-semibold text-stone-800" "Full specification source")
+        (h2 :class "text-2xl font-semibold text-stone-800" "Specification source")
         (p :class "text-xs text-stone-400 italic"
-          "The s-expression source below is the canonical test specification. "
-          "Any host that implements the five platform functions can evaluate it directly.")
+          (str "test-" spec-name ".sx")
+          " — the canonical test specification for this module.")
         (div :class "not-prose bg-stone-100 rounded-lg p-5 mx-auto max-w-3xl"
           (pre :class "text-sm leading-relaxed whitespace-pre-wrap break-words"
             (code (highlight spec-source "sx"))))))))
+
+
+;; ---------------------------------------------------------------------------
+;; Runners page
+;; ---------------------------------------------------------------------------
+
+(defcomp ~testing-runners-content ()
+  (~doc-page :title "Test Runners"
+    (div :class "space-y-8"
+
+      (div :class "space-y-4"
+        (p :class "text-lg text-stone-600"
+          "Three runners execute the same test specs on different hosts. Each injects the five platform functions and any per-spec extensions, then evaluates the SX source directly.")
+        (p :class "text-stone-600"
+          "All runners produce "
+          (a :href "https://testanything.org/" :class "text-violet-700 underline" "TAP")
+          " output and accept module names as arguments."))
+
+      ;; Node.js runner
+      (div :class "space-y-3"
+        (h2 :class "text-2xl font-semibold text-stone-800" "Node.js: run.js")
+        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
+          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "Usage")
+          (~doc-code :code
+            (highlight "# Run all specs\nnode shared/sx/tests/run.js\n\n# Run specific specs\nnode shared/sx/tests/run.js eval parser\n\n# Legacy mode (monolithic test.sx)\nnode shared/sx/tests/run.js --legacy" "bash")))
+        (p :class "text-stone-600 text-sm"
+          "Uses "
+          (code :class "text-violet-700 text-sm" "sx-browser.js")
+          " as the evaluator. Router tests use bootstrapped functions from "
+          (code :class "text-violet-700 text-sm" "Sx.splitPathSegments")
+          " etc. Render tests use "
+          (code :class "text-violet-700 text-sm" "Sx.renderToHtml")
+          "."))
+
+      ;; Python runner
+      (div :class "space-y-3"
+        (h2 :class "text-2xl font-semibold text-stone-800" "Python: run.py")
+        (div :class "rounded-lg border border-stone-200 bg-white p-5 space-y-3"
+          (h3 :class "text-sm font-medium text-stone-500 uppercase tracking-wide" "Usage")
+          (~doc-code :code
+            (highlight "# Run all specs\npython shared/sx/tests/run.py\n\n# Run specific specs\npython shared/sx/tests/run.py eval parser\n\n# Legacy mode (monolithic test.sx)\npython shared/sx/tests/run.py --legacy" "bash")))
+        (p :class "text-stone-600 text-sm"
+          "Uses the hand-written Python evaluator ("
+          (code :class "text-violet-700 text-sm" "evaluator.py")
+          "). Router tests import bootstrapped functions from "
+          (code :class "text-violet-700 text-sm" "sx_ref.py")
+          " because the hand-written evaluator's "
+          (code :class "text-violet-700 text-sm" "set!")
+          " doesn't propagate across lambda closure copies."))
+
+      ;; Browser runner
+      (div :class "space-y-3"
+        (h2 :class "text-2xl font-semibold text-stone-800" "Browser: sx-test-runner.js")
+        (p :class "text-stone-600"
+          "Runs in the browser on each test page. The spec source is embedded in a hidden textarea; the runner parses and evaluates it using the same "
+          (code :class "text-violet-700 text-sm" "sx-browser.js")
+          " that renders the page itself.")
+        (p :class "text-stone-600"
+          "This is the strongest proof of cross-host parity — the browser evaluator that users depend on is the same one running the tests."))
+
+      ;; Platform functions table
+      (div :class "space-y-3"
+        (h2 :class "text-2xl font-semibold text-stone-800" "Platform functions")
+        (div :class "overflow-x-auto rounded border border-stone-200"
+          (table :class "w-full text-left text-sm"
+            (thead (tr :class "border-b border-stone-200 bg-stone-100"
+              (th :class "px-3 py-2 font-medium text-stone-600" "Function")
+              (th :class "px-3 py-2 font-medium text-stone-600" "Scope")
+              (th :class "px-3 py-2 font-medium text-stone-600" "Purpose")))
+            (tbody
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "try-call")
+                (td :class "px-3 py-2" "All specs")
+                (td :class "px-3 py-2 text-stone-700" "Call a thunk, catch errors, return result dict"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "report-pass")
+                (td :class "px-3 py-2" "All specs")
+                (td :class "px-3 py-2 text-stone-700" "Report a passing test"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "report-fail")
+                (td :class "px-3 py-2" "All specs")
+                (td :class "px-3 py-2 text-stone-700" "Report a failing test with error message"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "push-suite")
+                (td :class "px-3 py-2" "All specs")
+                (td :class "px-3 py-2 text-stone-700" "Push suite name onto context stack"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "pop-suite")
+                (td :class "px-3 py-2" "All specs")
+                (td :class "px-3 py-2 text-stone-700" "Pop suite name from context stack"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "sx-parse")
+                (td :class "px-3 py-2" "Parser")
+                (td :class "px-3 py-2 text-stone-700" "Parse SX source to AST"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "sx-serialize")
+                (td :class "px-3 py-2" "Parser")
+                (td :class "px-3 py-2 text-stone-700" "Serialize AST back to SX source text"))
+              (tr :class "border-b border-stone-100"
+                (td :class "px-3 py-2 font-mono text-sm text-violet-700" "render-html")
+                (td :class "px-3 py-2" "Renderer")
+                (td :class "px-3 py-2 text-stone-700" "Parse SX source and render to HTML string"))))))
+
+      ;; Adding a new host
+      (div :class "rounded-lg border border-blue-200 bg-blue-50 p-5 space-y-3"
+        (h2 :class "text-lg font-semibold text-blue-900" "Adding a new host")
+        (ol :class "list-decimal list-inside text-blue-800 space-y-2 text-sm"
+          (li "Implement the 5 platform functions in your target language")
+          (li "Load " (code :class "text-sm" "test-framework.sx") " — it defines deftest/defsuite macros")
+          (li "Load the spec file(s) — the evaluator runs the tests automatically")
+          (li "Add per-spec platform functions if testing parser or renderer")
+          (li "Compare TAP output across hosts — divergences reveal platform-specific semantics"))))))
diff --git a/sx/sxc/pages/docs.sx b/sx/sxc/pages/docs.sx
index 7f2f672..777aefc 100644
--- a/sx/sxc/pages/docs.sx
+++ b/sx/sxc/pages/docs.sx
@@ -344,9 +344,6 @@
               :filename (get item "filename") :href (str "/specs/" (get item "slug"))
               :source (read-spec-file (get item "filename"))))
         extension-spec-items))
-    "testing" (~spec-testing-content
-      :spec-source (read-spec-file "test.sx")
-      :server-results (run-spec-tests))
     :else (let ((spec (find-spec slug)))
       (if spec
         (~spec-detail-content
@@ -516,3 +513,74 @@
     "glue-decoupling" (~plan-glue-decoupling-content)
     "social-sharing" (~plan-social-sharing-content)
     :else (~plans-index-content)))
+
+;; ---------------------------------------------------------------------------
+;; Testing section
+;; ---------------------------------------------------------------------------
+
+(defpage testing-index
+  :path "/testing/"
+  :auth :public
+  :layout (:sx-section
+    :section "Testing"
+    :sub-label "Testing"
+    :sub-href "/testing/"
+    :sub-nav (~section-nav :items testing-nav-items :current "Overview")
+    :selected "Overview")
+  :data (run-modular-tests "all")
+  :content (~testing-overview-content
+    :server-results server-results
+    :framework-source (read-spec-file "test-framework.sx")
+    :eval-source (read-spec-file "test-eval.sx")
+    :parser-source (read-spec-file "test-parser.sx")
+    :router-source (read-spec-file "test-router.sx")
+    :render-source (read-spec-file "test-render.sx")))
+
+(defpage testing-page
+  :path "/testing/<slug>"
+  :auth :public
+  :layout (:sx-section
+    :section "Testing"
+    :sub-label "Testing"
+    :sub-href "/testing/"
+    :sub-nav (~section-nav :items testing-nav-items
+               :current (find-current testing-nav-items slug))
+    :selected (or (find-current testing-nav-items slug) ""))
+  :data (case slug
+    "eval" (run-modular-tests "eval")
+    "parser" (run-modular-tests "parser")
+    "router" (run-modular-tests "router")
+    "render" (run-modular-tests "render")
+    :else (dict))
+  :content (case slug
+    "eval" (~testing-spec-content
+      :spec-name "eval"
+      :spec-title "Evaluator Tests"
+      :spec-desc "81 tests covering the core evaluator and all primitives — literals, arithmetic, comparison, strings, lists, dicts, predicates, special forms, lambdas, higher-order functions, components, macros, threading, and edge cases."
+      :spec-source (read-spec-file "test-eval.sx")
+      :framework-source (read-spec-file "test-framework.sx")
+      :server-results server-results)
+    "parser" (~testing-spec-content
+      :spec-name "parser"
+      :spec-title "Parser Tests"
+      :spec-desc "39 tests covering tokenization and parsing — integers, floats, strings, escape sequences, booleans, nil, keywords, symbols, lists, dicts, whitespace, comments, quote sugar, serialization, and round-trips."
+      :spec-source (read-spec-file "test-parser.sx")
+      :framework-source (read-spec-file "test-framework.sx")
+      :server-results server-results)
+    "router" (~testing-spec-content
+      :spec-name "router"
+      :spec-title "Router Tests"
+      :spec-desc "18 tests covering client-side route matching — path splitting, pattern parsing, segment matching, parameter extraction, and route table search."
+      :spec-source (read-spec-file "test-router.sx")
+      :framework-source (read-spec-file "test-framework.sx")
+      :server-results server-results)
+    "render" (~testing-spec-content
+      :spec-name "render"
+      :spec-title "Renderer Tests"
+      :spec-desc "23 tests covering HTML rendering — elements, attributes, void elements, boolean attributes, fragments, escaping, control flow, and component rendering."
+      :spec-source (read-spec-file "test-render.sx")
+      :framework-source (read-spec-file "test-framework.sx")
+      :server-results server-results)
+    "runners" (~testing-runners-content)
+    :else (~testing-overview-content
+      :server-results server-results)))
diff --git a/sx/sxc/pages/helpers.py b/sx/sxc/pages/helpers.py
index 150ca97..ddbc3f8 100644
--- a/sx/sxc/pages/helpers.py
+++ b/sx/sxc/pages/helpers.py
@@ -25,6 +25,7 @@ def _register_sx_helpers() -> None:
         "routing-analyzer-data": _routing_analyzer_data,
         "data-test-data": _data_test_data,
         "run-spec-tests": _run_spec_tests,
+        "run-modular-tests": _run_modular_tests,
     })
 
 
@@ -562,6 +563,199 @@ def _run_spec_tests() -> dict:
     }
 
 
+def _run_modular_tests(spec_name: str) -> dict:
+    """Run modular test specs against the Python SX evaluator.
+
+    spec_name: "eval", "parser", "router", "render", or "all".
+    Returns dict with server-results key containing results per spec.
+    """
+    import os
+    import time
+    from shared.sx.parser import parse_all
+    from shared.sx.evaluator import _eval, _trampoline
+    from shared.sx.types import Symbol, Keyword, Lambda, NIL
+
+    ref_dir = os.path.join(os.path.dirname(__file__), "..", "..", "shared", "sx", "ref")
+    if not os.path.isdir(ref_dir):
+        ref_dir = "/app/shared/sx/ref"
+
+    suite_stack: list[str] = []
+    passed = 0
+    failed = 0
+    test_num = 0
+    lines: list[str] = []
+
+    def try_call(thunk):
+        try:
+            _trampoline(_eval([thunk], env))
+            return {"ok": True}
+        except Exception as e:
+            return {"ok": False, "error": str(e)}
+
+    def report_pass(name):
+        nonlocal passed, test_num
+        test_num += 1
+        passed += 1
+        lines.append("ok " + str(test_num) + " - " + " > ".join(suite_stack + [name]))
+
+    def report_fail(name, error):
+        nonlocal failed, test_num
+        test_num += 1
+        failed += 1
+        full = " > ".join(suite_stack + [name])
+        lines.append("not ok " + str(test_num) + " - " + full)
+        lines.append("  # " + str(error))
+
+    def push_suite(name):
+        suite_stack.append(name)
+
+    def pop_suite():
+        suite_stack.pop()
+
+    def sx_parse(source):
+        return parse_all(source)
+
+    def sx_serialize(val):
+        if val is None or val is NIL:
+            return "nil"
+        if isinstance(val, bool):
+            return "true" if val else "false"
+        if isinstance(val, (int, float)):
+            return str(val)
+        if isinstance(val, str):
+            escaped = val.replace("\\", "\\\\").replace('"', '\\"')
+            return f'"{escaped}"'
+        if isinstance(val, Symbol):
+            return val.name
+        if isinstance(val, Keyword):
+            return f":{val.name}"
+        if isinstance(val, list):
+            inner = " ".join(sx_serialize(x) for x in val)
+            return f"({inner})"
+        if isinstance(val, dict):
+            parts = []
+            for k, v in val.items():
+                parts.append(f":{k}")
+                parts.append(sx_serialize(v))
+            return "{" + " ".join(parts) + "}"
+        return str(val)
+
+    def render_html(sx_source):
+        try:
+            from shared.sx.ref.sx_ref import render_to_html as _render_to_html
+        except ImportError:
+            return "<!-- render-to-html not available -->"
+        exprs = parse_all(sx_source)
+        render_env = dict(env)
+        result = ""
+        for expr in exprs:
+            result += _render_to_html(expr, render_env)
+        return result
+
+    def _call_sx(fn, args, caller_env):
+        if isinstance(fn, Lambda):
+            from shared.sx.evaluator import _call_lambda
+            return _trampoline(_call_lambda(fn, list(args), caller_env))
+        return fn(*args)
+
+    def _for_each_indexed(fn, coll):
+        if isinstance(fn, Lambda):
+            closure = fn.closure
+            for i, item in enumerate(coll or []):
+                for p, v in zip(fn.params, [i, item]):
+                    closure[p] = v
+                _trampoline(_eval(fn.body, closure))
+        else:
+            for i, item in enumerate(coll or []):
+                fn(i, item)
+        return NIL
+
+    env = {
+        "try-call": try_call,
+        "report-pass": report_pass,
+        "report-fail": report_fail,
+        "push-suite": push_suite,
+        "pop-suite": pop_suite,
+        "sx-parse": sx_parse,
+        "sx-serialize": sx_serialize,
+        "make-symbol": lambda name: Symbol(name),
+        "make-keyword": lambda name: Keyword(name),
+        "symbol-name": lambda sym: sym.name if isinstance(sym, Symbol) else str(sym),
+        "keyword-name": lambda kw: kw.name if isinstance(kw, Keyword) else str(kw),
+        "render-html": render_html,
+        "for-each-indexed": _for_each_indexed,
+        "dict-set!": lambda d, k, v: (d.__setitem__(k, v), NIL)[-1] if isinstance(d, dict) else NIL,
+        "dict-has?": lambda d, k: isinstance(d, dict) and k in d,
+        "dict-get": lambda d, k: d.get(k, NIL) if isinstance(d, dict) else NIL,
+        "append!": lambda lst, item: (lst.append(item), NIL)[-1] if isinstance(lst, list) else NIL,
+        "inc": lambda n: n + 1,
+    }
+
+    def eval_file(filename):
+        filepath = os.path.join(ref_dir, filename)
+        if not os.path.exists(filepath):
+            return
+        with open(filepath) as f:
+            src = f.read()
+        exprs = parse_all(src)
+        for expr in exprs:
+            _trampoline(_eval(expr, env))
+
+    SPECS = {
+        "eval": {"file": "test-eval.sx", "needs": []},
+        "parser": {"file": "test-parser.sx", "needs": ["sx-parse"]},
+        "router": {"file": "test-router.sx", "needs": []},
+        "render": {"file": "test-render.sx", "needs": ["render-html"]},
+    }
+
+    specs_to_run = list(SPECS.keys()) if spec_name == "all" else [spec_name]
+
+    t0 = time.monotonic()
+
+    # Load framework
+    eval_file("test-framework.sx")
+
+    for sn in specs_to_run:
+        spec = SPECS.get(sn)
+        if not spec:
+            continue
+
+        # Load router from bootstrap if needed
+        if sn == "router":
+            try:
+                from shared.sx.ref.sx_ref import (
+                    split_path_segments,
+                    parse_route_pattern,
+                    match_route_segments,
+                    match_route,
+                    find_matching_route,
+                    make_route_segment,
+                )
+                env["split-path-segments"] = split_path_segments
+                env["parse-route-pattern"] = parse_route_pattern
+                env["match-route-segments"] = match_route_segments
+                env["match-route"] = match_route
+                env["find-matching-route"] = find_matching_route
+                env["make-route-segment"] = make_route_segment
+            except ImportError:
+                eval_file("router.sx")
+
+        eval_file(spec["file"])
+
+    elapsed = round((time.monotonic() - t0) * 1000)
+
+    return {
+        "server-results": {
+            "passed": passed,
+            "failed": failed,
+            "total": passed + failed,
+            "elapsed-ms": elapsed,
+            "output": "\n".join(lines),
+            "spec": spec_name,
+        }
+    }
+
+
 def _data_test_data() -> dict:
     """Return test data for the client-side data rendering test page.