fix: register setUp only once, eliminating O(N²) accumulation. ~2x faster tests that can scale in 1 file#175
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jpohhhh wants to merge 2 commits intoBetterment:mainfrom
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fix: register setUp only once, eliminating O(N²) accumulation. ~2x faster tests that can scale in 1 file#175jpohhhh wants to merge 2 commits intoBetterment:mainfrom
jpohhhh wants to merge 2 commits intoBetterment:mainfrom
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Each call to goldenTest() was calling goldenTestAdapter.setUp(_setUpGoldenTests), appending a new setUp callback to the current test group every time. With N golden tests, all N callbacks ran before each of the 2N variant runs, producing 2N² total setUp executions (e.g. 20,000 for 100 tests). The fix guards the registration with a boolean so it happens exactly once. Benchmarked against a real project (442 golden tests, 63 files, --concurrency=1): | Metric | Before (0.13.0) | After (fix) | Improvement | |----------------|-----------------|-------------|-------------| | Peak RAM | 18.1 GB | 3.2 GB | 5.6× | | Wall time | 212 s (3:33) | 127 s (2:07)| 1.7× | | Test execution | 3:08 | 2:02 | 1.5× | | User CPU | 180.8 s | 85.8 s | 2.1× | | System CPU | 46.1 s | 17.7 s | 2.6× | | Page reclaims | 12.7M | 4.9M | 2.6× | The system CPU drop (46s → 18s) reflects kernel time spent on memory management (page faults, VM pressure) servicing the pathological allocation pattern. The O(N²) rapid-fire async setUp calls were starving the GC of idle time, preventing it from finalizing native rendering resources (Pictures, Images, surfaces) between test runs. A regression test is included that intercepts setUpFn/testWidgetsFn to prove the accumulation and its quadratic effect.
jpohhhh
requested review from
a team,
Kirpal,
btrautmann,
jeroen-meijer,
jolexxa and
marcossevilla
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Pull request overview
Addresses a test registration performance/memory issue where goldenTest() repeatedly registered a setUp callback, causing quadratic setUp executions as golden tests scaled within a file.
Changes:
- Adds a guard in
goldenTest()intended to register_setUpGoldenTestsviasetUponly once. - Adds a regression test that intercepts
setUpFn/testWidgetsFnto detect callback accumulation and assert linear scaling.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| lib/src/golden_test.dart | Introduces a global “register setUp once” guard around goldenTestAdapter.setUp(_setUpGoldenTests). |
| test/src/golden_test_set_up_accumulation_test.dart | Adds a regression test that records setUp registrations and simulates runtime executions to validate non-quadratic behavior. |
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| if (!_goldenTestSetUpRegistered) { | ||
| _goldenTestSetUpRegistered = true; | ||
| goldenTestAdapter.setUp(_setUpGoldenTests); | ||
| } |
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| final Set<String> _loadedFontFamilies = {}; | ||
| bool _goldenTestSetUpRegistered = false; | ||
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Comment on lines
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| // FIXED: only one setUp callback should be registered regardless | ||
| // of how many goldenTest() calls are made. | ||
| expect( | ||
| registeredSetUpCallbacks, | ||
| hasLength(1), | ||
| reason: 'goldenTest should register setUp at most once', | ||
| ); |
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Story
Description
Each call to goldenTest() was calling goldenTestAdapter.setUp(_setUpGoldenTests), appending a new setUp callback to the current test group every time. With N golden tests, all N callbacks ran before each of the 2N variant runs, producing 2N² total setUp executions (e.g. 20,000 for 100 tests).
The fix guards the registration with a boolean so it happens exactly once.
Benchmarked against a real project (442 golden tests, 63 files, --concurrency=1):
The system CPU drop (46s → 18s) reflects kernel time spent on memory management (page faults, VM pressure) servicing the pathological allocation pattern.
A regression test is included that intercepts setUpFn/testWidgetsFn to prove the accumulation and its quadratic effect.
Type of Change