Update tests to validate that projects/references are added properly.

src/EditorFeatures/Test/Workspaces/TestWorkspace.cs

@@ -280,6 +280,10 @@ public override bool CanApplyChange(ApplyChangesKind feature)
                 case ApplyChangesKind.ChangeAdditionalDocument:
                     return this.CanApplyChangeDocument;
 
+                case ApplyChangesKind.AddProjectReference:
+                case ApplyChangesKind.AddMetadataReference:
+                    return true;
+
                 default:
                     return false;
             }

src/EditorFeatures/Test2/Diagnostics/AbstractCrossLanguageUserDiagnosticTest.vb

@@ -53,11 +53,17 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics
                 Dim codeActions = diagnosticAndFix.Item2.Fixes.Select(Function(f) f.Action).ToList()
                 codeActions = MassageActions(codeActions)
                 Dim codeAction = codeActions(codeActionIndex)
-                Dim operations = Await codeAction.GetOperationsAsync(CancellationToken.None)
-                Dim edit = operations.OfType(Of ApplyChangesOperation)().First()
 
                 Dim oldSolution = workspace.CurrentSolution
-                Dim updatedSolution = edit.ChangedSolution
+                Dim operations = Await codeAction.GetOperationsAsync(CancellationToken.None)
+
+                For Each operation In operations
+                    If operation.ApplyDuringTests Then
+                        operation.Apply(workspace, CancellationToken.None)
+                    End If
+                Next
+
+                Dim updatedSolution = workspace.CurrentSolution
 
                 verifySolutions?.Invoke(oldSolution, updatedSolution)
 

src/Features/Core/Portable/AddImport/AddMetadataReferenceCodeActionOperation.cs

@@ -20,6 +20,8 @@ public AddMetadataReferenceCodeActionOperation(DocumentId documentId, PortableEx
                     _reference = reference;
                 }
 
+                internal override bool ApplyDuringTests => true;
+
                 public override void Apply(Workspace workspace, CancellationToken cancellationToken)
                 {
                     var service = workspace.Services.GetService<IAddImportUndoService>();

src/Features/Core/Portable/AddImport/AddProjectReferenceCodeActionOperation.cs

@@ -21,6 +21,8 @@ private class AddProjectReferenceCodeActionOperation : CodeActionOperation
                     _toProjectId = toProjectId;
                 }
 
+                internal override bool ApplyDuringTests => true;
+
                 public override void Apply(Workspace workspace, CancellationToken cancellationToken)
                 {
                     var service = workspace.Services.GetService<IAddImportUndoService>();

src/Features/Core/Portable/AddImport/IAddImportUndoService.cs

@@ -20,7 +20,7 @@ internal interface IAddImportUndoService : IWorkspaceService
             CancellationToken cancellationToken);
     }
 
-    [ExportWorkspaceService(typeof(IWorkspaceService)), Shared]
+    [ExportWorkspaceService(typeof(IAddImportUndoService)), Shared]
     internal class DefaultAddImportUndoService : IAddImportUndoService
     {
         public bool TryAddMetadataReference(

src/Workspaces/Core/Portable/CodeActions/Operations/ApplyChangesOperation.cs

@@ -41,6 +41,8 @@ public Solution ChangedSolution
             get { return _changedSolution; }
         }
 
+        internal override bool ApplyDuringTests => true;
+
         public override void Apply(Workspace workspace, CancellationToken cancellationToken)
         {
             this.Apply(workspace, new ProgressTracker(), cancellationToken);