Define an abstract DiffAlgorithm test framework

For certain tiny input sequences, every DiffAlgorithm should produce
exactly the same results, as there should be no ambiguity.  Package
these up in an abstract TestCase that algorithms can extend from in
order to perform basic validation of their implementation.

Since these tests are more complete than what we used to have for
the MyersDiff algorithm, throw away Johannes' tests and only use
this new package.

Change-Id: I9a044330887c849ad4c78aa5c7aa04c783c10252
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/AbstractDiffTestCase.java

@@ -0,0 +1,187 @@
+/*
+ * Copyright (C) 2010, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.diff;
+
+import java.io.UnsupportedEncodingException;
+
+import junit.framework.TestCase;
+
+public abstract class AbstractDiffTestCase extends TestCase {
+	public void testEmptyInputs() {
+		EditList r = diff(t(""), t(""));
+		assertTrue("is empty", r.isEmpty());
+	}
+
+	public void testCreateFile() {
+		EditList r = diff(t(""), t("AB"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(0, 0, 0, 2), r.get(0));
+	}
+
+	public void testDeleteFile() {
+		EditList r = diff(t("AB"), t(""));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(0, 2, 0, 0), r.get(0));
+	}
+
+	public void testDegenerate_InsertMiddle() {
+		EditList r = diff(t("ac"), t("aBc"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(1, 1, 1, 2), r.get(0));
+	}
+
+	public void testDegenerate_DeleteMiddle() {
+		EditList r = diff(t("aBc"), t("ac"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(1, 2, 1, 1), r.get(0));
+	}
+
+	public void testDegenerate_ReplaceMiddle() {
+		EditList r = diff(t("bCd"), t("bEd"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(1, 2, 1, 2), r.get(0));
+	}
+
+	public void testDegenerate_InsertsIntoMidPosition() {
+		EditList r = diff(t("aaaa"), t("aaXaa"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(2, 2, 2, 3), r.get(0));
+	}
+
+	public void testDegenerate_InsertStart() {
+		EditList r = diff(t("bc"), t("Abc"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(0, 0, 0, 1), r.get(0));
+	}
+
+	public void testDegenerate_DeleteStart() {
+		EditList r = diff(t("Abc"), t("bc"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(0, 1, 0, 0), r.get(0));
+	}
+
+	public void testDegenerate_InsertEnd() {
+		EditList r = diff(t("bc"), t("bcD"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(2, 2, 2, 3), r.get(0));
+	}
+
+	public void testDegenerate_DeleteEnd() {
+		EditList r = diff(t("bcD"), t("bc"));
+		assertEquals(1, r.size());
+		assertEquals(new Edit(2, 3, 2, 2), r.get(0));
+	}
+
+	public void testEdit_ReplaceCommonDelete() {
+		EditList r = diff(t("RbC"), t("Sb"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(0, 1, 0, 1), r.get(0));
+		assertEquals(new Edit(2, 3, 2, 2), r.get(1));
+	}
+
+	public void testEdit_CommonReplaceCommonDeleteCommon() {
+		EditList r = diff(t("aRbCd"), t("aSbd"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(1, 2, 1, 2), r.get(0));
+		assertEquals(new Edit(3, 4, 3, 3), r.get(1));
+	}
+
+	public void testEdit_MoveBlock() {
+		EditList r = diff(t("aYYbcdz"), t("abcdYYz"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(1, 3, 1, 1), r.get(0));
+		assertEquals(new Edit(6, 6, 4, 6), r.get(1));
+	}
+
+	public void testEdit_InvertBlocks() {
+		EditList r = diff(t("aYYbcdXXz"), t("aXXbcdYYz"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(1, 3, 1, 3), r.get(0));
+		assertEquals(new Edit(6, 8, 6, 8), r.get(1));
+	}
+
+	public void testEdit_UniqueCommonLargerThanMatchPoint() {
+		// We are testing 3 unique common matches, but two of
+		// them are consumed as part of the 1st's LCS region.
+		EditList r = diff(t("AbdeZ"), t("PbdeQR"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(0, 1, 0, 1), r.get(0));
+		assertEquals(new Edit(4, 5, 4, 6), r.get(1));
+	}
+
+	public void testEdit_CommonGrowsPrefixAndSuffix() {
+		// Here there is only one common unique point, but we can grow it
+		// in both directions to find the LCS in the middle.
+		EditList r = diff(t("AaabccZ"), t("PaabccR"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(0, 1, 0, 1), r.get(0));
+		assertEquals(new Edit(6, 7, 6, 7), r.get(1));
+	}
+
+	public void testEdit_DuplicateAButCommonUniqueInB() {
+		EditList r = diff(t("AbbcR"), t("CbcS"));
+		assertEquals(2, r.size());
+		assertEquals(new Edit(0, 2, 0, 1), r.get(0));
+		assertEquals(new Edit(4, 5, 3, 4), r.get(1));
+	}
+
+	public EditList diff(RawText a, RawText b) {
+		return algorithm().diff(RawTextComparator.DEFAULT, a, b);
+	}
+
+	protected abstract DiffAlgorithm algorithm();
+
+	public static RawText t(String text) {
+		StringBuilder r = new StringBuilder();
+		for (int i = 0; i < text.length(); i++) {
+			r.append(text.charAt(i));
+			r.append('\n');
+		}
+		try {
+			return new RawText(r.toString().getBytes("UTF-8"));
+		} catch (UnsupportedEncodingException e) {
+			throw new RuntimeException(e);
+		}
+	}
+}

org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/MyersDiffTest.java

@@ -1,6 +1,5 @@
 /*
- * Copyright (C) 2009, Johannes E. Schindelin
- * Copyright (C) 2009, Johannes Schindelin <johannes.schindelin@gmx.de>
+ * Copyright (C) 2010, Google Inc.
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
@@ -44,74 +43,9 @@
 
 package org.eclipse.jgit.diff;
 
-import junit.framework.TestCase;
-
-public class MyersDiffTest extends TestCase {
-	public void testAtEnd() {
-		assertDiff("HELLO", "HELL", " -4,1 +4,0");
-	}
-
-	public void testAtStart() {
-		assertDiff("Git", "JGit", " -0,0 +0,1");
-	}
-
-	public void testSimple() {
-		assertDiff("HELLO WORLD", "LOW",
-			" -0,3 +0,0 -5,1 +2,0 -7,4 +3,0");
-		// is ambiguous, could be this, too:
-		// " -0,2 +0,0 -3,1 +1,0 -5,1 +2,0 -7,4 +3,0"
-	}
-
-	public void assertDiff(String a, String b, String edits) {
-		EditList editList = MyersDiff.INSTANCE.diff(new CharCmp(),
-				toCharArray(a), toCharArray(b));
-		assertEquals(edits, toString(editList));
-	}
-
-	private static String toString(EditList list) {
-		StringBuilder builder = new StringBuilder();
-		for (Edit e : list)
-			builder.append(" -" + e.beginA
-					+ "," + (e.endA - e.beginA)
-				+ " +" + e.beginB + "," + (e.endB - e.beginB));
-		return builder.toString();
-	}
-
-	private static CharArray toCharArray(String s) {
-		return new CharArray(s);
-	}
-
-	protected static String toString(CharArray a, int begin, int end) {
-		return new String(a.array, begin, end - begin);
-	}
-
-	protected static String toString(CharArray a, CharArray b,
-			int x, int k) {
-		return "(" + x + "," + (k + x)
-			+ (x < 0 ? '<' :
-					(x >= a.array.length ?
-					 '>' : a.array[x]))
-			+ (k + x < 0 ? '<' :
-					(k + x >= b.array.length ?
-					 '>' : b.array[k + x]))
-			+ ")";
-	}
-
-	private static class CharArray extends Sequence {
-		char[] array;
-		public CharArray(String s) { array = s.toCharArray(); }
-		public int size() { return array.length; }
-	}
-
-	private static class CharCmp extends SequenceComparator<CharArray> {
-		@Override
-		public boolean equals(CharArray a, int ai, CharArray b, int bi) {
-			return a.array[ai] == b.array[bi];
-		}
-
-		@Override
-		public int hash(CharArray seq, int ptr) {
-			return seq.array[ptr];
-		}
+public class MyersDiffTest extends AbstractDiffTestCase {
+	@Override
+	protected DiffAlgorithm algorithm() {
+		return MyersDiff.INSTANCE;
 	}
 }

org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/PatienceDiffTest.java

@@ -43,102 +43,12 @@
 
 package org.eclipse.jgit.diff;
 
-import java.io.UnsupportedEncodingException;
-
-import junit.framework.TestCase;
-
-public class PatienceDiffTest extends TestCase {
-	public void testEmptyInputs() {
-		EditList r = diff(t(""), t(""));
-		assertTrue("is empty", r.isEmpty());
-	}
-
-	public void testCreateFile() {
-		EditList r = diff(t(""), t("AB"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(0, 0, 0, 2), r.get(0));
-	}
-
-	public void testDeleteFile() {
-		EditList r = diff(t("AB"), t(""));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(0, 2, 0, 0), r.get(0));
-	}
-
-	public void testDegenerate_InsertMiddle() {
-		EditList r = diff(t("ac"), t("aBc"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(1, 1, 1, 2), r.get(0));
-	}
-
-	public void testDegenerate_DeleteMiddle() {
-		EditList r = diff(t("aBc"), t("ac"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(1, 2, 1, 1), r.get(0));
-	}
-
-	public void testDegenerate_ReplaceMiddle() {
-		EditList r = diff(t("bCd"), t("bEd"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(1, 2, 1, 2), r.get(0));
-	}
-
-	public void testDegenerate_InsertsIntoMidPosition() {
-		EditList r = diff(t("aaaa"), t("aaXaa"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(2, 2, 2, 3), r.get(0));
-	}
-
-	public void testDegenerate_InsertStart() {
-		EditList r = diff(t("bc"), t("Abc"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(0, 0, 0, 1), r.get(0));
-	}
-
-	public void testDegenerate_DeleteStart() {
-		EditList r = diff(t("Abc"), t("bc"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(0, 1, 0, 0), r.get(0));
-	}
-
-	public void testDegenerate_InsertEnd() {
-		EditList r = diff(t("bc"), t("bcD"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(2, 2, 2, 3), r.get(0));
-	}
-
-	public void testDegenerate_DeleteEnd() {
-		EditList r = diff(t("bcD"), t("bc"));
-		assertEquals(1, r.size());
-		assertEquals(new Edit(2, 3, 2, 2), r.get(0));
-	}
-
-	public void testEdit_ReplaceCommonDelete() {
-		EditList r = diff(t("RbC"), t("Sb"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(0, 1, 0, 1), r.get(0));
-		assertEquals(new Edit(2, 3, 2, 2), r.get(1));
-	}
-
-	public void testEdit_CommonReplaceCommonDeleteCommon() {
-		EditList r = diff(t("aRbCd"), t("aSbd"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(1, 2, 1, 2), r.get(0));
-		assertEquals(new Edit(3, 4, 3, 3), r.get(1));
-	}
-
-	public void testEdit_MoveBlock() {
-		EditList r = diff(t("aYYbcdz"), t("abcdYYz"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(1, 3, 1, 1), r.get(0));
-		assertEquals(new Edit(6, 6, 4, 6), r.get(1));
-	}
-
-	public void testEdit_InvertBlocks() {
-		EditList r = diff(t("aYYbcdXXz"), t("aXXbcdYYz"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(1, 3, 1, 3), r.get(0));
-		assertEquals(new Edit(6, 8, 6, 8), r.get(1));
+public class PatienceDiffTest extends AbstractDiffTestCase {
+	@Override
+	protected DiffAlgorithm algorithm() {
+		PatienceDiff pd = new PatienceDiff();
+		pd.setFallbackAlgorithm(null);
+		return pd;
 	}
 
 	public void testEdit_NoUniqueMiddleSideA() {
@@ -153,57 +63,15 @@ public class PatienceDiffTest extends TestCase {
 		assertEquals(new Edit(1, 3, 1, 5), r.get(0));
 	}
 
-	public void testEdit_UniqueCommonLargerThanMatchPoint() {
-		// We are testing 3 unique common matches, but two of
-		// them are consumed as part of the 1st's LCS region.
-		EditList r = diff(t("AbdeZ"), t("PbdeQR"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(0, 1, 0, 1), r.get(0));
-		assertEquals(new Edit(4, 5, 4, 6), r.get(1));
-	}
-
-	public void testEdit_CommonGrowsPrefixAndSuffix() {
-		// Here there is only one common unique point, but we can grow it
-		// in both directions to find the LCS in the middle.
-		EditList r = diff(t("AaabccZ"), t("PaabccR"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(0, 1, 0, 1), r.get(0));
-		assertEquals(new Edit(6, 7, 6, 7), r.get(1));
-	}
-
-	public void testEdit_DuplicateAButCommonUniqueInB() {
-		EditList r = diff(t("AbbcR"), t("CbcS"));
-		assertEquals(2, r.size());
-		assertEquals(new Edit(0, 2, 0, 1), r.get(0));
-		assertEquals(new Edit(4, 5, 3, 4), r.get(1));
-	}
-
 	public void testPerformanceTestDeltaLength() {
 		String a = DiffTestDataGenerator.generateSequence(40000, 971, 3);
 		String b = DiffTestDataGenerator.generateSequence(40000, 1621, 5);
 		CharArray ac = new CharArray(a);
 		CharArray bc = new CharArray(b);
-		EditList r = new PatienceDiff().diff(new CharCmp(), ac, bc);
+		EditList r = algorithm().diff(new CharCmp(), ac, bc);
 		assertEquals(25, r.size());
 	}
 
-	private static EditList diff(RawText a, RawText b) {
-		return new PatienceDiff().diff(RawTextComparator.DEFAULT, a, b);
-	}
-
-	private static RawText t(String text) {
-		StringBuilder r = new StringBuilder();
-		for (int i = 0; i < text.length(); i++) {
-			r.append(text.charAt(i));
-			r.append('\n');
-		}
-		try {
-			return new RawText(r.toString().getBytes("UTF-8"));
-		} catch (UnsupportedEncodingException e) {
-			throw new RuntimeException(e);
-		}
-	}
-
 	private static class CharArray extends Sequence {
 		final char[] array;