Fix NavMenuHighlightsCurrentLocation in headless mode

src/Components/test/E2ETest/Tests/ComponentRenderingTestBase.cs

@@ -374,7 +374,7 @@ public void CanUseJsInteropToReferenceElements()
     [Fact]
     public void CanUseFocusExtensionToFocusElement()
     {
-        Browser.Manage().Window.Size = new System.Drawing.Size(100, 300);
+        Browser.SetWindowSize(100, 300);
         var appElement = Browser.MountTestComponent<ElementFocusComponent>();
 
         // y scroll position before click
@@ -408,7 +408,7 @@ public void CanUseFocusExtensionToFocusElement()
     [Fact]
     public void CanUseFocusExtensionToFocusSvgElement()
     {
-        Browser.Manage().Window.Size = new System.Drawing.Size(100, 300);
+        Browser.SetWindowSize(100, 300);
         var appElement = Browser.MountTestComponent<SvgFocusComponent>();
 
         var buttonElement = appElement.FindElement(By.Id("focus-button"));
@@ -430,7 +430,7 @@ public void CanUseFocusExtensionToFocusSvgElement()
     [Fact]
     public void CanUseFocusExtensionToFocusElementPreventScroll()
     {
-        Browser.Manage().Window.Size = new System.Drawing.Size(600, 600);
+        Browser.SetWindowSize(600, 600);
         var appElement = Browser.MountTestComponent<ElementFocusComponent>();
 
         var buttonElement = Browser.Exists(By.Id("focus-button-prevented"));

src/Components/test/E2ETest/Tests/StandaloneAppTest.cs

@@ -10,7 +10,7 @@
 namespace Microsoft.AspNetCore.Components.E2ETest.Tests;
 
 public class StandaloneAppTest
-    : ServerTestBase<BlazorWasmTestAppFixture<StandaloneApp.Program>>, IDisposable
+    : ServerTestBase<BlazorWasmTestAppFixture<StandaloneApp.Program>>
 {
     public StandaloneAppTest(
         BrowserFixture browserFixture,
@@ -22,6 +22,12 @@ public StandaloneAppTest(
 
     protected override void InitializeAsyncCore()
     {
+        // The sidebar is hidden if the screen is too narrow.
+        // Without setting the window size explicitly, visibility-sensitive properties (e.g. IWebElement.Text)
+        // and element finders (e.g. By.LinkText) can behave unexpectedly, causing assertions to fail.
+        // In particular, this happens in the headless mode (used when running without debugger).
+        Browser.SetWindowSize(1920, 1080);
+
         Navigate("/");
         WaitUntilLoaded();
     }
@@ -126,10 +132,12 @@ private void WaitUntilLoaded()
         Browser.NotEqual("Loading...", () => app.Text);
     }
 
-    public void Dispose()
+    public override Task DisposeAsync()
     {
         // Make the tests run faster by navigating back to the home page when we are done
         // If we don't, then the next test will reload the whole page before it starts
         Browser.Exists(By.LinkText("Home")).Click();
+
+        return base.DisposeAsync();
     }
 }

src/Shared/E2ETesting/BrowserTestBase.cs

@@ -16,6 +16,7 @@ public class BrowserTestBase : IClassFixture<BrowserFixture>, IAsyncLifetime
 
     private ExceptionDispatchInfo _exceptionDispatchInfo;
     private IWebDriver _browser;
+    private System.Drawing.Size? _originalWindowSize;
 
     public BrowserTestBase(BrowserFixture browserFixture, ITestOutputHelper output)
     {
@@ -49,8 +50,21 @@ public IWebDriver Browser
 
     public BrowserFixture BrowserFixture { get; }
 
-    public Task DisposeAsync()
+    public virtual Task DisposeAsync()
     {
+        try
+        {
+            if (_originalWindowSize.HasValue && _originalWindowSize.Value != Browser.Manage().Window.Size)
+            {
+                Browser.SetWindowSize(_originalWindowSize.Value.Width, _originalWindowSize.Value.Height);
+            }
+        }
+        catch (WebDriverException)
+        {
+            // An exception is thrown if the browser has been closed in the test.
+            // In that case we don't need to reset the window size.
+        }
+
         return Task.CompletedTask;
     }
 
@@ -78,6 +92,11 @@ protected void InitializeBrowser(string isolationContext)
             _asyncBrowser.Value = browser;
             _logs.Value = logs;
 
+            if (!_originalWindowSize.HasValue)
+            {
+                _originalWindowSize = browser.Manage().Window.Size;
+            }
+
             Browser = browser;
         }
         catch (Exception ex)

src/Shared/E2ETesting/WebDriverExtensions.cs

@@ -51,4 +51,11 @@ private static bool ShouldIgnore(LogEntry entry)
 
         return false;
     }
+
+    public static void SetWindowSize(this IWebDriver driver, int width, int height)
+    {
+        ArgumentNullException.ThrowIfNull(driver);
+
+        driver.Manage().Window.Size = new System.Drawing.Size(width, height);
+    }
 }