test(07-10): add debounced search unit test for UserAccessAuditViewModel

- Extended CreateViewModel helper to return (vm, auditMock, graphMock) 3-tuple
- Updated all 8 existing tests to use _ discard for the new graphMock slot
- Added Test 9: SearchQuery_debounced_calls_SearchUsersAsync verifying that
  setting SearchQuery to "Ali" calls SearchUsersAsync after 300ms debounce
- All 9 ViewModel tests pass; full suite 177 passed / 22 skipped

SharepointToolbox.Tests/ViewModels/UserAccessAuditViewModelTests.cs

@@ -41,8 +41,8 @@ public class UserAccessAuditViewModelTests
         string upn = "alice@contoso.com") =>
         new(display, upn, upn);
 
-    /// <summary>Creates a ViewModel wired with a mock IUserAccessAuditService.</summary>
+    /// <summary>Creates a ViewModel wired with mock services.</summary>
-    private static (UserAccessAuditViewModel vm, Mock<IUserAccessAuditService> auditMock)
+    private static (UserAccessAuditViewModel vm, Mock<IUserAccessAuditService> auditMock, Mock<IGraphUserSearchService> graphMock)
         CreateViewModel(IReadOnlyList<UserAccessEntry>? auditResult = null)
     {
         var mockAudit = new Mock<IUserAccessAuditService>();
@@ -65,7 +65,7 @@ public class UserAccessAuditViewModelTests
             mockSession.Object,
             NullLogger<FeatureViewModelBase>.Instance);
 
-        return (vm, mockAudit);
+        return (vm, mockAudit, mockGraph);
     }
 
     // ── Test 1: RunOperation calls AuditUsersAsync ────────────────────────────
@@ -73,7 +73,7 @@ public class UserAccessAuditViewModelTests
     [Fact]
     public async Task RunOperation_calls_AuditUsersAsync()
     {
-        var (vm, auditMock) = CreateViewModel();
+        var (vm, auditMock, _) = CreateViewModel();
 
         vm.SelectedUsers.Add(MakeUser());
         vm.SelectedSites.Add(new SiteInfo("https://contoso.sharepoint.com", "Contoso"));
@@ -102,7 +102,7 @@ public class UserAccessAuditViewModelTests
             MakeEntry(userLogin: "bob@contoso.com")
         };
 
-        var (vm, _) = CreateViewModel(entries);
+        var (vm, _, _) = CreateViewModel(entries);
 
         vm.SelectedUsers.Add(MakeUser());
         vm.SelectedSites.Add(new SiteInfo("https://contoso.sharepoint.com", "Contoso"));
@@ -124,7 +124,7 @@ public class UserAccessAuditViewModelTests
             MakeEntry(userLogin: "bob@contoso.com",   siteUrl: "https://contoso.sharepoint.com/sites/s1", isHighPrivilege: true)
         };
 
-        var (vm, _) = CreateViewModel(entries);
+        var (vm, _, _) = CreateViewModel(entries);
 
         vm.SelectedUsers.Add(MakeUser());
         vm.SelectedSites.Add(new SiteInfo("https://contoso.sharepoint.com", "Contoso"));
@@ -142,7 +142,7 @@ public class UserAccessAuditViewModelTests
     public async Task OnTenantSwitched_resets_state()
     {
         var entries = new List<UserAccessEntry> { MakeEntry() };
-        var (vm, _) = CreateViewModel(entries);
+        var (vm, _, _) = CreateViewModel(entries);
 
         // Populate state
         vm.SelectedUsers.Add(MakeUser());
@@ -172,7 +172,7 @@ public class UserAccessAuditViewModelTests
     [Fact]
     public void OnGlobalSitesChanged_updates_selected_sites()
     {
-        var (vm, _) = CreateViewModel();
+        var (vm, _, _) = CreateViewModel();
         var sites = new List<SiteInfo>
         {
             new("https://contoso.sharepoint.com/sites/hr", "HR"),
@@ -190,7 +190,7 @@ public class UserAccessAuditViewModelTests
     [Fact]
     public void OnGlobalSitesChanged_skipped_when_override()
     {
-        var (vm, _) = CreateViewModel();
+        var (vm, _, _) = CreateViewModel();
 
         // Add a local site and set the override flag via reflection
         var localSite = new SiteInfo("https://contoso.sharepoint.com/sites/local", "Local");
@@ -218,7 +218,7 @@ public class UserAccessAuditViewModelTests
     [Fact]
     public void CanExport_false_when_no_results()
     {
-        var (vm, _) = CreateViewModel();
+        var (vm, _, _) = CreateViewModel();
 
         // Results is empty by default
         Assert.Empty(vm.Results);
@@ -232,7 +232,7 @@ public class UserAccessAuditViewModelTests
     public async Task CanExport_true_when_has_results()
     {
         var entries = new List<UserAccessEntry> { MakeEntry() };
-        var (vm, _) = CreateViewModel(entries);
+        var (vm, _, _) = CreateViewModel(entries);
 
         vm.SelectedUsers.Add(MakeUser());
         vm.SelectedSites.Add(new SiteInfo("https://contoso.sharepoint.com", "Contoso"));
@@ -243,4 +243,49 @@ public class UserAccessAuditViewModelTests
         Assert.True(vm.ExportCsvCommand.CanExecute(null));
         Assert.True(vm.ExportHtmlCommand.CanExecute(null));
     }
+
+    // ── Test 9: Debounced search triggers SearchUsersAsync ───────────────────
+
+    [Fact]
+    public async Task SearchQuery_debounced_calls_SearchUsersAsync()
+    {
+        var graphResults = new List<GraphUserResult>
+        {
+            new("Alice Smith", "alice@contoso.com", "alice@contoso.com")
+        };
+
+        var (vm, _, graphMock) = CreateViewModel();
+
+        graphMock
+            .Setup(s => s.SearchUsersAsync(
+                It.IsAny<string>(),
+                It.Is<string>(q => q == "Ali"),
+                It.IsAny<int>(),
+                It.IsAny<CancellationToken>()))
+            .ReturnsAsync(graphResults);
+
+        // Set a TenantProfile so _currentProfile is non-null
+        var profile = new TenantProfile
+        {
+            Name = "Test",
+            TenantUrl = "https://contoso.sharepoint.com",
+            ClientId = "test-client-id"
+        };
+        WeakReferenceMessenger.Default.Send(new TenantSwitchedMessage(profile));
+
+        // Act: set SearchQuery which triggers OnSearchQueryChanged → DebounceSearchAsync
+        vm.SearchQuery = "Ali";
+
+        // Wait longer than 300ms debounce to allow async fire-and-forget to complete
+        await Task.Delay(600);
+
+        // Assert: SearchUsersAsync was called with the query
+        graphMock.Verify(
+            s => s.SearchUsersAsync(
+                It.IsAny<string>(),
+                "Ali",
+                It.IsAny<int>(),
+                It.IsAny<CancellationToken>()),
+            Times.Once);
+    }
 }