diff --git a/java/java-tests/testSrc/com/intellij/psi/PsiDocumentManager2Test.java b/java/java-tests/testSrc/com/intellij/psi/PsiDocumentManager2Test.java
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+++ b/java/java-tests/testSrc/com/intellij/psi/PsiDocumentManager2Test.java
@@ -0,0 +1,130 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package com.intellij.psi;
+
+import com.intellij.codeHighlighting.BackgroundEditorHighlighter;
+import com.intellij.codeInsight.daemon.DaemonCodeAnalyzer;
+import com.intellij.ide.highlighter.XmlLikeFileType;
+import com.intellij.lang.StdLanguages;
+import com.intellij.lang.java.JavaLanguage;
+import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.application.ReadAction;
+import com.intellij.openapi.editor.Document;
+import com.intellij.openapi.fileEditor.FileDocumentManager;
+import com.intellij.openapi.fileEditor.FileEditor;
+import com.intellij.openapi.fileEditor.TextEditor;
+import com.intellij.openapi.fileEditor.impl.text.AsyncEditorLoader;
+import com.intellij.openapi.fileEditor.impl.text.TextEditorProvider;
+import com.intellij.openapi.util.Disposer;
+import com.intellij.openapi.vfs.VirtualFile;
+import com.intellij.psi.impl.PsiManagerEx;
+import com.intellij.testFramework.PlatformTestCase;
+import com.intellij.testFramework.PsiTestCase;
+import com.intellij.util.LocalTimeCounter;
+import com.intellij.util.ObjectUtils;
+import com.intellij.util.ui.UIUtil;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import javax.swing.*;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+
+@PlatformTestCase.WrapInCommand
+public class PsiDocumentManager2Test extends PsiTestCase {
+  public void testUnregisteredFileType() {
+    class MyFileType extends XmlLikeFileType {
+      private MyFileType() {
+        super(StdLanguages.XML);
+      }
+
+      @Override
+      @NotNull
+      public String getName() {
+        return "MY";
+      }
+
+      @Override
+      @NotNull
+      public String getDefaultExtension() {
+        return "my";
+      }
+
+      @Override
+      @NotNull
+      public String getDescription() {
+        return "my own";
+      }
+
+      @Override
+      @Nullable
+      public Icon getIcon() {
+        return null;
+      }
+    }
+    PsiFile file = PsiFileFactory.getInstance(myProject).createFileFromText("DummyFile.my", new MyFileType(), "<gggg></gggg>", LocalTimeCounter.currentTime(), true);
+    Document document = ObjectUtils.assertNotNull(PsiDocumentManager.getInstance(myProject).getDocument(file));
+
+    assertTrue(document.isWritable());
+    assertTrue(file.getVirtualFile().getFileType() instanceof MyFileType);
+    assertTrue(DaemonCodeAnalyzer.getInstance(getProject()).isHighlightingAvailable(file));
+  }
+
+  public void testPsiToDocSyncInNonPhysicalFile() {
+    PsiJavaFile file = (PsiJavaFile)PsiFileFactory.getInstance(myProject).createFileFromText("a.java", JavaLanguage.INSTANCE, "class Foo {}", false, false);
+
+    Document document = FileDocumentManager.getInstance().getDocument(file.getViewProvider().getVirtualFile());
+    assertNotNull(document);
+
+    file.getClasses()[0].getModifierList().setModifierProperty(PsiModifier.PUBLIC, true);
+
+    assertEquals("public class Foo {}", document.getText());
+    assertFalse(PsiDocumentManager.getInstance(myProject).isUncommited(document));
+  }
+
+  public void testDocumentCanSuddenlyBecomeUncommittedIfLightAndTextEditorBackgroundHighlighterDoesntFreakOutAtThatMoment() throws Exception {
+    ApplicationManager.getApplication().assertIsDispatchThread();
+    assertEmpty(PsiDocumentManager.getInstance(getProject()).getUncommittedDocuments());
+    PsiJavaCodeReferenceCodeFragment fragment =
+      JavaCodeFragmentFactory.getInstance(getProject()).createReferenceCodeFragment("xxx", null, false, true);
+
+    VirtualFile file = fragment.getViewProvider().getVirtualFile();
+    Document document = ObjectUtils.assertNotNull(FileDocumentManager.getInstance().getDocument(file));
+
+    assertNotNull(file);
+    FileViewProvider provider = fragment.getViewProvider();
+    assertNotNull(provider.getPsi(fragment.getLanguage()));
+    assertNotNull(provider);
+    assertSame(provider, ((PsiManagerEx)getPsiManager()).getFileManager().findCachedViewProvider(file));
+
+    Future<Document> modification = ApplicationManager.getApplication().executeOnPooledThread(() -> ReadAction.compute(() -> {
+      document.insertString(0, "c");
+
+      Document uncommitted = assertOneElement(PsiDocumentManager.getInstance(getProject()).getUncommittedDocuments());
+      assertSame(document, uncommitted);
+
+      return document;
+    }));
+    PsiFile toHighlight = createFile("x.txt", "text");
+    FileEditor fileEditor = TextEditorProvider.getInstance().createEditor(getProject(), toHighlight.getVirtualFile());
+    Disposer.register(getTestRootDisposable(), fileEditor);
+    CompletableFuture<?> passesCreated = new CompletableFuture<>();
+    AsyncEditorLoader.performWhenLoaded(((TextEditor)fileEditor).getEditor(), () -> {
+      try {
+        BackgroundEditorHighlighter highlighter = fileEditor.getBackgroundHighlighter();
+        highlighter.createPassesForEditor(); // check didn't crash in TextEditorBackgroundHighlighter.getPasses() isCommitted() check
+        passesCreated.complete(null);
+      }
+      catch (Throwable e) {
+        passesCreated.completeExceptionally(e);
+      }
+    });
+
+    long start = System.currentTimeMillis();
+    while (!PsiDocumentManager.getInstance(getProject()).isCommitted(document) || !modification.isDone() || !passesCreated.isDone()) {
+      UIUtil.dispatchAllInvocationEvents();
+      assertTrue(System.currentTimeMillis() < start + 100 * 1000);
+    }
+    modification.get();
+    passesCreated.get();
+  }
+}