test(centralui): TreeView keyboard-activation test + document preventDefault scope (T36a review)

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/TreeView.razor

@@ -59,6 +59,9 @@ else
                           @onclick="() => ToggleExpand(key)"
                           @onclick:stopPropagation
                           @onkeydown="(e) => OnToggleKey(e, key)"
+                          @* preventDefault suppresses Space-bar page scroll on activation (intended for a role=button).
+                             It also suppresses Arrow-key default scroll while the toggle itself has focus — acceptable,
+                             as the chevron is Tab-navigated and Blazor offers no per-key conditional preventDefault. *@
                           @onkeydown:preventDefault><i class="bi bi-chevron-right"></i></span>
                 }
                 else

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Shared/AccessibilityTests.cs

@@ -88,6 +88,38 @@ public class AccessibilityTests : BunitContext
         Assert.StartsWith("Collapse", labelAfterExpand!);
     }
 
+    // ── Test 3: TreeView keyboard activation (Enter / Space) ──────────────────
+
+    [Fact]
+    public void TreeViewToggle_EnterKey_TogglesExpanded()
+    {
+        var cut = RenderTreeView();
+
+        var toggle = cut.Find(".tv-toggle");
+        Assert.Equal("false", toggle.GetAttribute("aria-expanded"));
+
+        // Fire Enter on the toggle — should expand the branch.
+        toggle.TriggerEvent("onkeydown", new Microsoft.AspNetCore.Components.Web.KeyboardEventArgs { Key = "Enter" });
+
+        var expandedToggle = cut.Find(".tv-toggle");
+        Assert.Equal("true", expandedToggle.GetAttribute("aria-expanded"));
+    }
+
+    [Fact]
+    public void TreeViewToggle_SpaceKey_TogglesExpanded()
+    {
+        var cut = RenderTreeView();
+
+        var toggle = cut.Find(".tv-toggle");
+        Assert.Equal("false", toggle.GetAttribute("aria-expanded"));
+
+        // Fire Space on the toggle — should expand the branch.
+        toggle.TriggerEvent("onkeydown", new Microsoft.AspNetCore.Components.Web.KeyboardEventArgs { Key = " " });
+
+        var expandedToggle = cut.Find(".tv-toggle");
+        Assert.Equal("true", expandedToggle.GetAttribute("aria-expanded"));
+    }
+
     // ── Test 2: ToastNotification live-region regression lock ─────────────────
 
     [Fact]