Type of Request

bug

Infrastructure Environment

LUCI, Github

What is happening?

I've seen this happen several times now.

In a given PR, newly added unit tests will pass in presubmit. After the PR is approved and lands, some of those newly added unit tests fail, and the change is reverted.

I've seen this happen on:

• Introduce ChipAnimationStyle to override default chips animations durations #149245
  • https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20web_tests_2/17525/overview
• TreeSliver & associated classes #147171
  • This one in particular did not start to break the tree on its own unit tests until several commits after the PR landed
  • https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8745951578924749729/+/u/run_test.dart_for_framework_tests_shard_and_subshard_impeller/stdout
• sliverGridDelegate mainAxisExtent add assert #148470
  • https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20web_canvaskit_tests_7_last/14617/overview

It sounds like @christopherfujino has a lead on why this might be happening: #149245 (comment)

There were also some golden file failures in postsubmit earlier today that we weren't sure how they were getting in. If the golden file tests did not execute in presubmit, like is suspected above, then this is also the likely cause of the unexpected golden files at head.

Steps to reproduce

See linked builds above

Expected results

Tests run in both presubmit and postsubmit, reflecting the same result.