feat: Lock random seeds in the flutter/tests customer testing run - #4052
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The customer testing script now passes a fixed RANDOM_SEED define to flutter test so that the run is deterministic. To make that work, the testRandom helper offsets a fixed seed by the repeat index instead of reusing it, testWidgetsRandom honors the define too, and the two tests that created an unseeded Random directly now seed it from the environment.
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Picks up flame-engine/flame#4051, which fixes the solveQuadratic random test tolerance that made the customer test fail for some seeds, and flame-engine/flame#4052, which pins the randomized tests to a fixed seed in the customer testing run so it stays deterministic.
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Description
The flutter/tests customer testing run exists to catch regressions in flutter/flutter, so it should be deterministic. Randomized tests with fresh seeds on every run (see #4051 for a recent example) can make it fail for reasons that have nothing to do with the framework change under test.
scripts/customer_testing.dartnow passes--dart-define=RANDOM_SEED=<fixed>toflutter test. TheRANDOM_SEEDdefine was already read bytestRandominflame_test, but a few things had to change for it to be usable across a whole run:testRandomoffsets a fixed seed by the repeat index, sorepeatCount: 3still runs three distinct cases instead of the same one three times. This applies to theseed:parameter as well, and the first repeat still uses the seed as given, so reproducing a failure from the test output works as before.testWidgetsRandomnow honors the define too. It previously ignored it.Random()directly (the fixed aspect ratio viewport auto-resizing test and the opacity effect fade out test) now seed it throughseedFromEnvironment, so they are deterministic under the define and unchanged otherwise.random_test_testassertion that consecutive seeds differ is skipped when the define is set, since that is exactly what the define turns off. A new test covers the repeat offset behavior.Flame's own CI keeps running the randomized tests with fresh seeds, so randomized coverage is unchanged there.
Verified locally with
flutter testinflame_testand on the affectedflametests, both with and without--dart-define=RANDOM_SEED=20260922. With the define, the test names show consecutive seeds per repeat and everything passes.Checklist
docsand added dartdoc comments with///.examplesordocs.Breaking Change?
Related Issues
Follow-up to #4051 and flutter/tests#493.