From 98b0104c7bf526c6fe0c8ddb8b0a059be82f5bc7 Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Sun, 28 Jun 2026 17:48:47 +0000
Subject: [PATCH] erlang: send_after deadline-ordering + cancel-of-fired tests
 (T3+T4, 769/769)
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T3 — concurrent timers fire in deadline order, not schedule order
(scheduler jumps the clock to the earliest pending deadline each
time the runnable queue drains). T4 — cancel_timer on an
already-fired timer returns the atom false.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 lib/erlang/scoreboard.json     |  6 ++---
 lib/erlang/scoreboard.md       |  4 ++--
 lib/erlang/tests/send_after.sx | 40 ++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/lib/erlang/scoreboard.json b/lib/erlang/scoreboard.json
index 3f06c462..ede12189 100644
--- a/lib/erlang/scoreboard.json
+++ b/lib/erlang/scoreboard.json
@@ -1,7 +1,7 @@
 {
   "language": "erlang",
-  "total_pass": 766,
-  "total": 766,
+  "total_pass": 769,
+  "total": 769,
   "suites": [
     {"name":"tokenize","pass":62,"total":62,"status":"ok"},
     {"name":"parse","pass":52,"total":52,"status":"ok"},
@@ -14,6 +14,6 @@
     {"name":"fib","pass":8,"total":8,"status":"ok"},
     {"name":"ffi","pass":37,"total":37,"status":"ok"},
     {"name":"vm","pass":78,"total":78,"status":"ok"},
-    {"name":"send_after","pass":5,"total":5,"status":"ok"}
+    {"name":"send_after","pass":8,"total":8,"status":"ok"}
   ]
 }
diff --git a/lib/erlang/scoreboard.md b/lib/erlang/scoreboard.md
index e83b5e9a..7afac274 100644
--- a/lib/erlang/scoreboard.md
+++ b/lib/erlang/scoreboard.md
@@ -1,6 +1,6 @@
 # Erlang-on-SX Scoreboard
 
-**Total: 766 / 766 tests passing**
+**Total: 769 / 769 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
@@ -15,7 +15,7 @@
 | ✅ | fib | 8 | 8 |
 | ✅ | ffi | 37 | 37 |
 | ✅ | vm | 78 | 78 |
-| ✅ | send_after | 5 | 5 |
+| ✅ | send_after | 8 | 8 |
 
 
 Generated by `lib/erlang/conformance.sh`.
diff --git a/lib/erlang/tests/send_after.sx b/lib/erlang/tests/send_after.sx
index 1a83eff8..7b150f18 100644
--- a/lib/erlang/tests/send_after.sx
+++ b/lib/erlang/tests/send_after.sx
@@ -78,3 +78,43 @@
        receive late -> got after 50 -> none end")
     :name)
   "none")
+
+;; ── T3 — multiple timers fire in deadline order, not schedule order ──
+;; `b` is scheduled first (deadline 80) but `a` second (deadline 20).
+;; Two plain receives drain the mailbox in arrival order — and arrival
+;; is governed by deadline, so the first message out is `a`.
+(er-sa-test
+  "T3 timers fire in deadline order"
+  (er-format-value
+    (sa-ev
+      "erlang:send_after(80, self(), b),
+       erlang:send_after(20, self(), a),
+       X = receive M1 -> M1 end,
+       Y = receive M2 -> M2 end,
+       {X, Y}"))
+  "{a,b}")
+
+;; A selective receive on `a` matches the earlier-deadline timer even
+;; though `b` was scheduled first.
+(er-sa-test
+  "T3 selective receive picks earliest deadline"
+  (get
+    (sa-ev
+      "erlang:send_after(80, self(), b),
+       erlang:send_after(20, self(), a),
+       receive a -> first end")
+    :name)
+  "first")
+
+;; ── T4 — cancel_timer on an already-fired timer returns false ──────
+;; Once `x` has been received the timer has fired; cancelling its ref
+;; now yields the atom `false`.
+(er-sa-test
+  "T4 cancel of fired timer is false"
+  (get
+    (sa-ev
+      "Ref = erlang:send_after(20, self(), x),
+       receive x -> ok end,
+       erlang:cancel_timer(Ref)")
+    :name)
+  "false")