diff --git a/java/java-tests/testSrc/com/intellij/lexer/LayeredLexerTest.java b/java/java-tests/testSrc/com/intellij/lexer/LayeredLexerTest.java
new file mode 100644
index 000000000000..21bc0650d6e0
--- /dev/null
+++ b/java/java-tests/testSrc/com/intellij/lexer/LayeredLexerTest.java
@@ -0,0 +1,110 @@
+package com.intellij.lexer;
+
+import com.intellij.pom.java.LanguageLevel;
+import com.intellij.psi.JavaTokenType;
+import com.intellij.psi.tree.IElementType;
+import junit.framework.TestCase;
+
+/**
+ * @author max
+ */
+public class LayeredLexerTest extends TestCase {
+  public void testInTheMiddle() throws Exception {
+    Lexer lexer = setupLexer("s=\"abc\\ndef\";");
+
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"abc", nextToken(lexer));
+    assertEquals("\\n", nextToken(lexer));
+    assertEquals("def\"", nextToken(lexer));
+    assertEquals(";", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+  public void testModification() throws Exception {
+    Lexer lexer = setupLexer("s=\"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\";");
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\"", nextToken(lexer));
+    assertEquals(";", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+
+    lexer.start(lexer.getBufferSequence(), 2, lexer.getBufferEnd(), (short) 1);
+    assertEquals("\"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\"", nextToken(lexer));
+    assertEquals(";", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+
+  public void testInTheAtStartup() throws Exception {
+    Lexer lexer = setupLexer("s=\"\\ndef\";");
+
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"", nextToken(lexer));
+    assertEquals("\\n", nextToken(lexer));
+    assertEquals("def\"", nextToken(lexer));
+    assertEquals(";", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+  public void testInTheAtEnd() throws Exception {
+    Lexer lexer = setupLexer("s=\"abc\\n\";");
+
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"abc", nextToken(lexer));
+    assertEquals("\\n", nextToken(lexer));
+    assertEquals("\"", nextToken(lexer));
+    assertEquals(";", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+  public void testNonTerminated() throws Exception {
+    Lexer lexer = setupLexer("s=\"abc\\n");
+
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"abc", nextToken(lexer));
+    assertEquals("\\n", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+  public void testNonTerminated2() throws Exception {
+    Lexer lexer = setupLexer("s=\"abc\\");
+
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"abc", nextToken(lexer));
+    assertEquals("\\", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+  public void testUnicode() throws Exception {
+    Lexer lexer = setupLexer("s=\"\\uFFFF\";");
+    assertEquals("s", nextToken(lexer));
+    assertEquals("=", nextToken(lexer));
+    assertEquals("\"", nextToken(lexer));
+    assertEquals("\\uFFFF", nextToken(lexer));
+    assertEquals("\"", nextToken(lexer));
+    assertEquals(";", nextToken(lexer));
+    assertEquals(null, lexer.getTokenType());
+  }
+
+  private Lexer setupLexer(String text) {
+    LayeredLexer lexer = new LayeredLexer(new JavaLexer(LanguageLevel.JDK_1_3));
+    lexer.registerSelfStoppingLayer(new StringLiteralLexer('\"', JavaTokenType.STRING_LITERAL),
+                                    new IElementType[]{JavaTokenType.STRING_LITERAL},
+                                    IElementType.EMPTY_ARRAY);
+
+    lexer.start(text);
+    return lexer;
+  }
+
+  private String nextToken(Lexer lexer) {
+    assertTrue(lexer.getTokenType() != null);
+    final String s = lexer.getBufferSequence().subSequence(lexer.getTokenStart(), lexer.getTokenEnd()).toString();
+    lexer.advance();
+    return s;
+  }
+}
diff --git a/platform/platform-tests/testSrc/com/intellij/diff/SelectedBlockHistoryTest.java b/platform/platform-tests/testSrc/com/intellij/diff/SelectedBlockHistoryTest.java
new file mode 100644
index 000000000000..cf8f1c0c0ea3
--- /dev/null
+++ b/platform/platform-tests/testSrc/com/intellij/diff/SelectedBlockHistoryTest.java
@@ -0,0 +1,225 @@
+package com.intellij.diff;
+
+import com.intellij.util.ArrayUtil;
+import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.diff.FilesTooBigForDiffException;
+import junit.framework.TestCase;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * author: lesya
+ */
+
+public class SelectedBlockHistoryTest extends TestCase {
+
+  public void test1() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "52", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test2() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "52", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test3() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test4() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test5() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test6() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test7() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{}
+    );
+  }
+
+  public void test8() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"44", "4", "5", "6", "66"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test9() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"44", "4", "55", "6", "66"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test10() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"0.5", "1", "3", "3.5"},
+        new String[]{"4", "5","5.5", "6"},
+        new String[]{"6,5", "7", "8", "9", "9.5"},
+
+        new String[]{"+0.5", "1", "2", "3", "3.5+", "3.5++"},
+        new String[]{"4", "5","5.5+", "6"},
+        new String[]{"+6,5","++6,5",  "7", "9", "9.5+", "9.5++"}
+    );
+  }
+
+  public void test11() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"a", "a"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"b"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test12() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{},
+        new String[]{"7", "8", "9"},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+  public void test13() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"},
+
+        new String[]{},
+        new String[]{"4", "52", "6"},
+        new String[]{}
+    );
+  }
+
+  public void test14() throws FilesTooBigForDiffException {
+    doTest(
+        new String[]{},
+        new String[]{"4", "52", "6"},
+        new String[]{},
+
+        new String[]{"1", "2", "3"},
+        new String[]{"4", "5", "6"},
+        new String[]{"7", "8", "9"}
+    );
+  }
+
+
+  public void testContent(){
+    Block block = new Block("0\n1\n2\n3\n4\n5\n6", 3, 6);
+    String blockContent = block.getBlockContent();
+    assertEquals("3\n4\n5\n6", blockContent);
+
+    block = new Block("0\n1\n2\n3\n4\n5\n6\n", 3, 6);
+    blockContent = block.getBlockContent();
+    assertEquals("3\n4\n5\n6", blockContent);
+
+  }
+
+  private void doTest(
+      String[] beforePrevBlock,
+      String[] prevBlock,
+      String[] afterPrevBlock,
+      String[] beforeBlock,
+      String[] block,
+      String[] afterBlock) throws FilesTooBigForDiffException {
+
+    String[] prevVersion = composeVersion(beforePrevBlock, prevBlock, afterPrevBlock);
+    String[] currentVersion = composeVersion(beforeBlock, block, afterBlock);
+    FindBlock findBlock = new FindBlock(prevVersion,
+        new Block(currentVersion, beforeBlock.length, beforeBlock.length + block.length - 1));
+
+    Block actualBlock = findBlock.getBlockInThePrevVersion();
+    Block expectedBlock = new Block(prevVersion,beforePrevBlock.length, beforePrevBlock.length + prevBlock.length - 1);
+
+    assertEquals(expectedBlock, actualBlock);
+
+  }
+
+  private String[] composeVersion(String[] beforeBlock, String[] block, String[] afterBlock) {
+    List beforeList = new ArrayList();
+    ContainerUtil.addAll(beforeList, beforeBlock);
+    ContainerUtil.addAll(beforeList, block);
+    ContainerUtil.addAll(beforeList, afterBlock);
+    return (String[])ArrayUtil.toStringArray(beforeList);
+
+  }
+}