Add additional test.

src/EditorFeatures/CSharpTest/Squiggles/ErrorSquiggleProducerTests.cs

@@ -153,6 +153,36 @@ public async Task SemanticErrorReported()
             Assert.Contains("Bar", (string)firstSpan.Tag.ToolTipContent, StringComparison.Ordinal);
         }
 
+        [WpfFact, Trait(Traits.Feature, Traits.Features.ErrorSquiggles)]
+        public async Task TestNoErrorsAfterDocumentRemoved()
+        {
+            using (var workspace = CSharpWorkspaceFactory.CreateWorkspaceFromLines("class"))
+            using (var wrapper = new DiagnosticTaggerWrapper(workspace))
+            {
+                var tagger = wrapper.TaggerProvider.CreateTagger<IErrorTag>(workspace.Documents.First().GetTextBuffer());
+                using (var disposable = tagger as IDisposable)
+                {
+                    await wrapper.WaitForTags().ConfigureAwait(true);
+
+                    var snapshot = workspace.Documents.First().GetTextBuffer().CurrentSnapshot;
+                    var spans = tagger.GetTags(snapshot.GetSnapshotSpanCollection()).ToList();
+
+                    // Initially, while the buffer is associated with a Document, we should get
+                    // error squiggles.
+                    Assert.True(spans.Count > 0);
+
+                    // Now remove the document.
+                    workspace.CloseDocument(workspace.Documents.First().Id);
+                    workspace.OnDocumentRemoved(workspace.Documents.First().Id);
+                    await wrapper.WaitForTags().ConfigureAwait(true);
+                    spans = tagger.GetTags(snapshot.GetSnapshotSpanCollection()).ToList();
+
+                    // And we should have no errors for this document.
+                    Assert.True(spans.Count == 0);
+                }
+            }
+        }
+
         [WpfFact, Trait(Traits.Feature, Traits.Features.ErrorSquiggles)]
         public async Task TestNoErrorsAfterProjectRemoved()
         {
@@ -167,6 +197,8 @@ public async Task TestNoErrorsAfterProjectRemoved()
                     var snapshot = workspace.Documents.First().GetTextBuffer().CurrentSnapshot;
                     var spans = tagger.GetTags(snapshot.GetSnapshotSpanCollection()).ToList();
 
+                    // Initially, while the buffer is associated with a Document, we should get
+                    // error squiggles.
                     Assert.True(spans.Count > 0);
 
                     // Now remove the project.