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Resolves https://github.com/flutter/flutter/issues/154628
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As a contributor, I would expect resources related to testing to be located in the [/docs/contributing/testing](https://github.com/flutter/flutter/tree/master/docs/contributing/testing) directory. This PR adds a page to that directory geared toward helping new contributors.
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I've noticed that in `team-framework` triage meetings, comments along the lines of "could you take a look at the failing checks?" are a regular occurrence.
I believe we could save quite a bit of effort by changing this:
> [**Understanding a LUCI build failure**](a5ca16ea94/docs/infra/Understanding-a-LUCI-build-failure.md
)
to this:
> [**Flutter wiki â How to fix failing checks**](https://github.com/nate-thegrate/flutter/blob/fix-checks-wiki-page/docs/contributing/testing/Fix-failing-checks.md)
139 lines
5.7 KiB
Markdown
139 lines
5.7 KiB
Markdown

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# How to fix a PR's failing checks
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### tree-status
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Unlike other checks, **tree-status** isn't tied to the pull request:
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instead, it shows whether checks are passing in the main branch.\
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Failures can happen for a variety of reasons and should be addressed
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before anything else is merged in.
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**What to do:** Once [review requirements](../Tree-hygiene.md#getting-a-code-review)
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are met and all other checks are passing, a reviewer will add the
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[**`autosubmit`**](../../infra/Landing-Changes-With-Autosubmit.md) label,
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and then a bot will merge the PR once **tree-status** succeeds.
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<br>
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### Google testing
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A Google testing failure could be a flake ([see below](#flaking)), or it
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might be due to changes in the PR (See
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[Understanding Google Testing](../../infra/Understanding-Google-Testing.md)
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for more info).
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Google employees can view the test output and give feedback accordingly.
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**What to do:** If 2 weeks have gone by and nobody's looked into it,
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feel free to [reach out on Discord](../Chat.md).
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<br>
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### ci.yaml validation
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In order for checks to run correctly, the [.ci.yaml](../../../.ci.yaml)
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file needs to stay in sync with the base branch.
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**What to do:** This check failure can be fixed by applying the latest changes
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from master.\
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(The [Tree hygiene](../Tree-hygiene.md#using-git) page recommends updating
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via rebase, rather than a merge commit.)
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<br>
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## A bug in the PR
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Oftentimes, a change inadvertently breaks expected behavior.\
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When this happens, usually the best way to find out what's wrong is to
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[**view the test output**](#view-the-test-output).
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If a **customer_testing** check is unsuccessful, it's a signal that something in the
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[Flutter customer test registry](https://github.com/flutter/tests/) has failed.
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This includes [package tests](../../ecosystem/testing/Understanding-Packages-tests.md)
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along with other tests from open-source Flutter projects.\
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If a pull request requires an update to those external tests, it qualifies as a
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[**breaking change**](../Tree-hygiene.md#handling-breaking-changes);
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please avoid those when possible.
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If **Linux Analyze** fails, it's likely that one or more changes in the PR
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violated a [linter rule](https://dart.dev/lints/).\
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Consider reviewing the steps outlined in
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[setting up the framework dev environment](../../Setting-up-the-Framework-development-environment.md)
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so that most of these problems get caught in static analysis right away.
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> [!NOTE]
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> All Dart code is run through static analysis:
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> this includes markdown code snippets in doc comments!
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>
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> See [Hixie's Natural Log](https://ln.hixie.ch/?start=1660174115) for more details.
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<br>
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### View the test output
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Click on **Details** for the failing test, and then click
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**View more details on flutter-dashboard**.
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The full test output is linked at the bottom of the page.
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<br>
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Often, there will be a message that resembles the one below:
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```
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══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
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The following TestFailure was thrown running a test:
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Expected: exactly one matching candidate
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Actual: _TextWidgetFinder:<Found 0 widgets with text
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"AsyncSnapshot<String>(ConnectionState.waiting, null, null, null)": []>
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Which: means none were found but one was expected
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When the exception was thrown, this was the stack:
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#4 main.<anonymous closure>.<anonymous closure> (…/packages/flutter/test/widgets/async_test.dart:115:7)
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<asynchronous suspension>
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#5 testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:189:15)
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<asynchronous suspension>
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#6 TestWidgetsFlutterBinding._runTestBody (package:flutter_test/src/binding.dart:1032:5)
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<asynchronous suspension>
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<asynchronous suspension>
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(elided one frame from package:stack_trace)
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This was caught by the test expectation on the following line:
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file:///b/s/w/ir/x/w/flutter/packages/flutter/test/widgets/async_test.dart line 115
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The test description was:
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gracefully handles transition from null future
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════════════════════════════════════════════════════════════════════════════════════════════════════
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```
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From there, it's just a matter of finding the failing test,
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[running it locally](./Running-and-writing-tests.md),
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and figuring out how to fix it!
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<br>
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### Flaking
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A check might "flake", or randomly fail, for a variety of reasons.
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Sometimes a flake resolves itself after changes are pushed to re-trigger
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the checks. Consider [performing a rebase](#ciyaml-validation) to include
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the latest changes from the main branch.
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Flakes often happen due to **infra errors**.
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For information on how to view and report infrastructure bugs, see the
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[infra failure overview](../../infra/Understanding-a-LUCI-build-failure.md#overview-of-an-infra-failure-build).
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