[webview_flutter_web] Migrate integration tests to package:web.

[ditman]

This PR:

• Fixes a DOM timing issue that was preventing the Legacy Widget from building.
• Makes the integration_tests for the package less flaky, now that they seem to be timing out unexpectedly in CI.

Issues

• Fixes [webview_flutter_web] Legacy mode accessing DOM before it's ready. flutter#151693
• Should prevent this flake from happening: bad / good (Linux_web web_platform_tests_shard_3 stable)

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or this PR is exempt from CHANGELOG changes.
• 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.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[ditman]

Now the non-legacy test should actually do something in CI. The legacy one is only left as a manual check. No coverage is lost, since neither of the tests were actually verifying anything earlier (the bug that is being fixed here should have been caught by a functional legacy test!)

This should also ease the Linux_web web_platform_tests_shard_3 flakes. In my machine this PR seems to not flake, unlike what's currently in the repo!

[ditman]

Nah, this is still flaking :/

• https://ci.chromium.org/ui/p/flutter/builders/try/Linux_web%20web_platform_tests_shard_1%20master/9401/overview

[ditman]

$ flutter --version
Flutter 3.22.2 • channel stable • git@github.com:flutter/flutter.git
Framework • revision 761747bfc5 (5 weeks ago) • 2024-06-05 22:15:13 +0200
Engine • revision edd8546116
Tools • Dart 3.4.3 • DevTools 2.34.3
$ flutter clean; run_integration_test.sh | ts -s
00:00:03 
00:00:03 ============================================================
00:00:03 || Running for packages/webview_flutter/webview_flutter_web
00:00:03 ============================================================
00:00:03 
00:00:03 Starting chromedriver on port 4444
00:00:03 Running command: "flutter drive -d web-server --web-port=7357 --browser-name=chrome --web-renderer=canvaskit --driver test_driver/integration_test.dart --target integration_test/webview_flutter_test.dart" in /work/flutter/packages/packages/webview_flutter/webview_flutter_web/example
00:00:03 Resolving dependencies...
00:00:04 Downloading packages...
00:00:04   collection 1.18.0 (1.19.0 available)
00:00:04   leak_tracker 10.0.4 (10.0.5 available)
00:00:04   leak_tracker_flutter_testing 3.0.3 (3.0.5 available)
00:00:04   material_color_utilities 0.8.0 (0.12.0 available)
00:00:04   meta 1.12.0 (1.15.0 available)
00:00:04   platform 3.1.4 (3.1.5 available)
00:00:04   string_scanner 1.2.0 (1.3.0 available)
00:00:04   test_api 0.7.0 (0.7.3 available)
00:00:04   vm_service 14.2.1 (14.2.4 available)
00:00:04 Got dependencies!
00:00:04 9 packages have newer versions incompatible with dependency constraints.
00:00:04 Try `flutter pub outdated` for more information.
00:00:04 Launching integration_test/webview_flutter_test.dart on Web Server in debug mode...
00:00:31 Waiting for connection from debug service on Web Server...         26.3s
00:00:31 integration_test/webview_flutter_test.dart is being served at http://localhost:7357
00:00:31 The web-server device requires the Dart Debug Chrome extension for debugging. Consider using the Chrome or Edge devices for an improved development workflow.
00:00:38 All tests passed.
00:00:38 Application finished.
00:00:39 Stopping chromedriver
00:00:39 
00:00:39 
00:00:39 ------------------------------------------------------------
00:00:39 Run overview:
00:00:39   packages/webview_flutter/webview_flutter_web - ran
00:00:39 
00:00:39 Ran for 1 package(s)
00:00:39 
00:00:39 
00:00:39 No issues found!

vs CI. 🤷

[ditman]

The problem seems to stem from some DDC modules not being ready/available when the app starts. It doesn't always reproduce, but it can be seen when the app fails to start with --no-headless flag set:

(I've seen it also fail with a very similar trace, but complaining about IntegrationTestWidgetsFlutterBinding not being defined... Smells like a race condition! Are we attempting to start the app before the compilation is ready??)

I wonder if testing in --profile mode would yield better results (in general)

[ditman]

I wonder if testing in --profile mode would yield better results (in general)

It probably does, but we can't use that mode, because asserts don't work in --profile, and we have some tests that check that assertions are thrown.