Fix NavMenuHighlightsCurrentLocation in headless mode

[oroztocil]

This test is failing in CI and when run locally without debugger. The reason is that in the headless mode the window width is too small and the sidebar UI is hidden. This causes visibility-sensitive properties such as IWebElement.Text to return empty strings for hidden elements from the sidebar, causing assertions to fail.

The PR solves the issue by explicitly setting the window size for this particular test. We can discuss if the preferred solution is to set the window size globally when creating the test browser in the headless mode. Alternatively, the test could be fixed by using a visibility-independent API such as IWebElement.GetDomProperty("innerText") for reading the relevant values. However, using a realistic window size seems more appropriate for an E2E test.

The PR also adds the IWebDriver.SetWindowSize extension method. A few existing cases where window size is manipulated were refactored to use this method in order to make such cases more discoverable.

Fixes #54497

[Copilot]

Pull Request Overview

This PR fixes a failing test in headless mode by addressing viewport size issues that cause sidebar elements to be hidden, leading to empty text properties in assertions.

Key changes:

• Adds a SetWindowSize extension method for IWebDriver to standardize window size manipulation
• Sets explicit window size (1920x1080) in the failing NavMenuHighlightsCurrentLocation test
• Refactors existing window size manipulations to use the new extension method

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/Shared/E2ETesting/WebDriverExtensions.cs	Adds new SetWindowSize extension method for consistent window size management
src/Components/test/E2ETest/Tests/StandaloneAppTest.cs	Sets explicit window size to prevent sidebar visibility issues in headless mode
src/Components/test/E2ETest/Tests/ComponentRenderingTestBase.cs	Refactors three existing tests to use the new SetWindowSize extension method

[ilonatommy]

I do not see any tests that would manipulate with window size or would rely on a specific view, so setting it globally for all sounds like a good idea.

[oroztocil]

I do not see any tests that would manipulate with window size or would rely on a specific view, so setting it globally for all sounds like a good idea.

There are few in src/Components/test/E2ETest/Tests/ComponentRenderingTestBase.cs - the one's that I updated to use the new extension method. However, if I understand it correctly, there would be no problem to have a default window size explicitly set because these tests will override the size (just as they do now). So the question is if there are some tests that implicitly rely on no value being set by default.

[akoeplinger]

I assume this doesn't fail if the physical screen size is lower than this right?

[oroztocil]

Based on docs and empirical testing:

• In GUI mode the size is clamped so that the window fits into the screen.
• In headless mode the window size is set to whatever is specified and the rest of the test executes fine. (I tried 10000x10000 and had no issues.)

[oroztocil]

We also decided to add a mechanism for resetting the window size between individual tests to prevent unexpected dependencies between tests in the future.

[oroztocil]

/backport to release/10.0

[github-actions]

Started backporting to release/10.0: https://github.com/dotnet/aspnetcore/actions/runs/17613935455