diff --git a/src/Tests/Testing.Common/Testing/CodeVerifier.cs b/src/Tests/Testing.Common/Testing/CodeVerifier.cs
index 14b81ef52a..c721edf68f 100644
--- a/src/Tests/Testing.Common/Testing/CodeVerifier.cs
+++ b/src/Tests/Testing.Common/Testing/CodeVerifier.cs
@@ -312,7 +312,12 @@ internal static (Document document, ImmutableArray<ExpectedDocument> expectedDoc
                 for (int i = 0; i < additionalFiles.Length; i++)
                 {
                     Document additionalDocument = project.AddDocument(AppendNumberToFileName(options.DocumentName, i + 2), SourceText.From(additionalFiles[i].Source));
-                    expectedDocuments.Add(new ExpectedDocument(additionalDocument.Id, additionalFiles[i].ExpectedSource));
+
+                    string expectedSource = additionalFiles[i].ExpectedSource;
+
+                    if (expectedSource != null)
+                        expectedDocuments.Add(new ExpectedDocument(additionalDocument.Id, expectedSource));
+
                     project = additionalDocument.Project;
                 }
 
diff --git a/src/Tests/Testing.Common/Testing/CompilerDiagnosticFixVerifier.cs b/src/Tests/Testing.Common/Testing/CompilerDiagnosticFixVerifier.cs
index 50776256ac..609c946a05 100644
--- a/src/Tests/Testing.Common/Testing/CompilerDiagnosticFixVerifier.cs
+++ b/src/Tests/Testing.Common/Testing/CompilerDiagnosticFixVerifier.cs
@@ -180,7 +180,7 @@ public async Task VerifyNoFixAsync(
 
             using (Workspace workspace = new AdhocWorkspace())
             {
-                (Document document, ImmutableArray<ExpectedDocument> expectedDocuments) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options);
+                (Document document, ImmutableArray<ExpectedDocument> _) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options);
 
                 Compilation compilation = await document.Project.GetCompilationAsync(cancellationToken);
 
diff --git a/src/Tests/Testing.Common/Testing/DiagnosticVerifier.cs b/src/Tests/Testing.Common/Testing/DiagnosticVerifier.cs
index ca1ca9063f..213c752807 100644
--- a/src/Tests/Testing.Common/Testing/DiagnosticVerifier.cs
+++ b/src/Tests/Testing.Common/Testing/DiagnosticVerifier.cs
@@ -73,6 +73,9 @@ public async Task VerifyDiagnosticAsync(
                 {
                     VerifyDiagnostics(data, analyzer, expectedDiagnostics, diagnostics, cancellationToken);
                 }
+
+                if (expectedDocuments.Any())
+                    await VerifyAdditionalDocumentsAsync(document.Project, expectedDocuments, cancellationToken);
             }
 
             static IEnumerable<Diagnostic> FilterDiagnostics(
@@ -119,7 +122,7 @@ public async Task VerifyNoDiagnosticAsync(
 
             using (Workspace workspace = new AdhocWorkspace())
             {
-                (Document document, ImmutableArray<ExpectedDocument> expectedDocuments) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options, data.Descriptor);
+                (Document document, ImmutableArray<ExpectedDocument> _) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options, data.Descriptor);
 
                 SyntaxTree tree = await document.GetSyntaxTreeAsync();
 
@@ -342,7 +345,7 @@ private async Task VerifyNoFixAsync(
 
             using (Workspace workspace = new AdhocWorkspace())
             {
-                (Document document, ImmutableArray<ExpectedDocument> expectedDocuments) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options, data.Descriptor);
+                (Document document, ImmutableArray<ExpectedDocument> _) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options, data.Descriptor);
 
                 Compilation compilation = await document.Project.GetCompilationAsync(cancellationToken);
 
diff --git a/src/Tests/Testing.Common/Testing/RefactoringVerifier.cs b/src/Tests/Testing.Common/Testing/RefactoringVerifier.cs
index 2cd475a50f..319449c3f1 100644
--- a/src/Tests/Testing.Common/Testing/RefactoringVerifier.cs
+++ b/src/Tests/Testing.Common/Testing/RefactoringVerifier.cs
@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
@@ -99,6 +100,9 @@ public async Task VerifyRefactoringAsync(
                     VerifyNoNewCompilerDiagnostics(compilerDiagnostics, newCompilerDiagnostics, options);
 
                     await VerifyExpectedDocument(expected, document, cancellationToken);
+
+                    if (expectedDocuments.Any())
+                        await VerifyAdditionalDocumentsAsync(document.Project, expectedDocuments, cancellationToken);
                 }
             }
         }
@@ -128,7 +132,7 @@ public async Task VerifyNoRefactoringAsync(
 
             using (Workspace workspace = new AdhocWorkspace())
             {
-                (Document document, ImmutableArray<ExpectedDocument> expectedDocuments) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options);
+                (Document document, ImmutableArray<ExpectedDocument> _) = CreateDocument(workspace.CurrentSolution, data.Source, data.AdditionalFiles, options);
 
                 SemanticModel semanticModel = await document.GetSemanticModelAsync(cancellationToken);