Move sliver_utils to test/widgets to fix rendering→widgets layering

[MohamedGawdat]

Part of #177412

Summary

The first commit on this branch swapped a legacy material.dart import in packages/flutter/test/rendering/sliver_utils.dart for widgets.dart. Reviewer feedback (gemini-code-assist) flagged a layering concern: a file under test/rendering/ should not depend on package:flutter/widgets.dart.

Since MockSliverToBoxAdapter extends SingleChildRenderObjectWidget, the widgets dependency is structural and cannot be removed. Both consumers of this utility (sliver_main_axis_group_test.dart, sliver_cross_axis_group_test.dart) already live in test/widgets/, so the second commit moves the file there and updates the import paths.

Changes:

• Move packages/flutter/test/rendering/sliver_utils.dart → packages/flutter/test/widgets/sliver_utils.dart
• Update import in packages/flutter/test/widgets/sliver_main_axis_group_test.dart
• Update import in packages/flutter/test/widgets/sliver_cross_axis_group_test.dart

No behavior change.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

Tests

• ./bin/dart analyze packages/flutter/test/widgets/sliver_utils.dart packages/flutter/test/widgets/sliver_main_axis_group_test.dart packages/flutter/test/widgets/sliver_cross_axis_group_test.dart
• ./bin/flutter test packages/flutter/test/widgets/sliver_main_axis_group_test.dart packages/flutter/test/widgets/sliver_cross_axis_group_test.dart

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

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[gemini-code-assist]

Code Review

This pull request updates sliver_utils.dart by replacing the material library import with the widgets library. A review comment identifies an architectural layering violation where the rendering layer now depends on the widgets layer and suggests moving the utility file to the widgets test directory to maintain proper repository boundaries.

[MohamedGawdat]

Test exemption note: this is a no-semantic-change refactor — the file is moved between test directories and two import paths are updated, with no behavior change. The existing tests in sliver_main_axis_group_test.dart and sliver_cross_axis_group_test.dart continue to pass and exercise the same code paths. Per Tree Hygiene, refactors of this kind are not auto-exempt; happy to request an explicit test-exempt: <reason> from @test-exemption-reviewer on Discord if a reviewer prefers.

[Piinks]

LGTM!

[auto-submit]

auto label is removed for flutter/flutter/185472, Failed to enqueue flutter/flutter/185472 with HTTP 400: Pull request Required status check "Merge Queue Guard" is expected..

[auto-submit]

auto label is removed for flutter/flutter/185472, Failed to enqueue flutter/flutter/185472 with HTTP 400: Pull request Required status check "Merge Queue Guard" is expected..