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rose-ash/lib/persist/tests/project.sx
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persist: projections — fold stream into read model, incremental resume + 9 tests
project.sx: projection state {:value :seq}; persist/project folds the whole
stream, persist/project-resume folds only the tail so read models update
incrementally. Pure step (value event)->value. 37/37.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-06 18:34:52 +00:00

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; Phase 2 — projections: fold a stream into a read model, resume incrementally.
(persist-test
"project empty stream returns seed value"
(persist/project-fold
(persist/open)
"s"
(fn (acc e) (+ acc 1))
0)
0)
(persist-test
"project empty stream seq is 0"
(persist/project-seq
(persist/project (persist/open) "s" (fn (a e) a) 0))
0)
(persist-test
"project counts events"
(let
((b (persist/open)))
(begin
(persist/append b "s" "x" 0 {})
(persist/append b "s" "x" 0 {})
(persist/append b "s" "x" 0 {})
(persist/project-fold
b
"s"
(fn (acc e) (+ acc 1))
0)))
3)
(persist-test
"project sums event data"
(let
((b (persist/open)))
(begin
(persist/append b "ledger" "credit" 0 {:amt 10})
(persist/append b "ledger" "credit" 1 {:amt 5})
(persist/append b "ledger" "debit" 2 {:amt 3})
(persist/project-fold
b
"ledger"
(fn
(bal e)
(if
(equal? (persist/event-type e) "credit")
(+ bal (get (persist/event-data e) :amt))
(- bal (get (persist/event-data e) :amt))))
0)))
12)
(persist-test
"project tracks last seq"
(let
((b (persist/open)))
(begin
(persist/append b "s" "x" 0 {})
(persist/append b "s" "x" 0 {})
(persist/project-seq (persist/project b "s" (fn (a e) a) 0))))
2)
(persist-test
"resume folds only the tail"
(let
((b (persist/open)))
(begin
(persist/append b "s" "x" 0 {})
(persist/append b "s" "x" 0 {})
(let
((p1 (persist/project b "s" (fn (acc e) (+ acc 1)) 0)))
(begin
(persist/append b "s" "x" 0 {})
(persist/project-value
(persist/project-resume
b
"s"
(fn (acc e) (+ acc 1))
p1))))))
3)
(persist-test
"resume with no new events is a no-op"
(let
((b (persist/open)))
(begin
(persist/append b "s" "x" 0 {})
(let
((p1 (persist/project b "s" (fn (acc e) (+ acc 1)) 0)))
(persist/project-value
(persist/project-resume b "s" (fn (acc e) (+ acc 1)) p1)))))
1)
(persist-test
"resume advances seq"
(let
((b (persist/open)))
(begin
(persist/append b "s" "x" 0 {})
(let
((p1 (persist/project b "s" (fn (a e) a) 0)))
(begin
(persist/append b "s" "x" 0 {})
(persist/append b "s" "x" 0 {})
(persist/project-seq
(persist/project-resume b "s" (fn (a e) a) p1))))))
3)
(persist-test
"full project equals seed-resume from zero"
(let
((b (persist/open)))
(begin
(persist/append b "s" "x" 0 {})
(persist/append b "s" "x" 0 {})
(equal?
(persist/project b "s" (fn (acc e) (+ acc 1)) 0)
(persist/project-resume
b
"s"
(fn (acc e) (+ acc 1))
{:value 0 :seq 0}))))
true)