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[Repo Assist] test: add SideEffects module to TaskSeq.FirstLastDefault.Tests.fs - #403
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dsyme merged 2 commits intoMay 1, 2026
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Add SideEffects tests for firstOrDefault and lastOrDefault, covering: - firstOrDefault stops consuming after the first element (matches head behaviour) - firstOrDefault executes side effects that occur before the first yield - lastOrDefault fully drains the sequence (matches last/tryLast behaviour) - TestSideEffectTaskSeq theory variants for both functions 58 tests now pass for the FirstLastDefault suite (19 new). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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May 1, 2026 16:54
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🤖 This is an automated pull request from Repo Assist, an AI assistant.
Summary
TaskSeq.FirstLastDefault.Tests.fshadEmptySeqandImmutablemodules but was missing aSideEffectsmodule, unlike most other test files in the suite.This PR adds a
SideEffectsmodule with 5 new test scenarios (19 new test runs when expanded with Theory data):New tests
firstOrDefault __special-case__ prove it does not read beyond first yield: Verifies thatfirstOrDefaultstops consuming the sequence immediately after yielding the first element — code after the firstyieldis never executed (matcheshead/tryHeadsemantics, sincefirstOrDefaultdelegates totryHead).firstOrDefault __special-case__ prove early side effect is executed: Verifies that side effects before the first yield do execute, but side effects after the first yield do not.lastOrDefault __special-case__ prove it reads the entire sequence: Verifies thatlastOrDefaultfully drains the sequence — all side effects (including those between yields) are executed before returning the last value.firstOrDefault returns first item in a side-effect sequence(TestSideEffectTaskSeqvariants): Across all 8 side-effect sequence variants,firstOrDefaultreturns1on the first enumeration and a different value on the second (because mutable state has advanced).lastOrDefault returns last item and exhausts the sequence(TestSideEffectTaskSeqvariants): Across all 8 variants,lastOrDefaultreturns10on the first full enumeration and20on the second — confirming the sequence is fully consumed each time.Test growth
Test Status
dotnet build src/FSharp.Control.TaskSeq.Test -c Release— succeeded (0 warnings, 0 errors)dotnet test --filter FirstLastDefault -c Release— 58 passed, 0 faileddotnet fantomas src/.../TaskSeq.FirstLastDefault.Tests.fs— unchanged