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1   /*
2    * Copyright (C) 2010, Google Inc. and others
3    *
4    * This program and the accompanying materials are made available under the
5    * terms of the Eclipse Distribution License v. 1.0 which is available at
6    * https://www.eclipse.org/org/documents/edl-v10.php.
7    *
8    * SPDX-License-Identifier: BSD-3-Clause
9    */
10  
11  package org.eclipse.jgit.diff;
12  
13  import static org.junit.Assert.assertEquals;
14  
15  import org.junit.Test;
16  
17  
18  public class HistogramDiffTest extends AbstractDiffTestCase {
19  	@Override
20  	protected HistogramDiff algorithm() {
21  		HistogramDiff hd = new HistogramDiff();
22  		hd.setFallbackAlgorithm(null);
23  		return hd;
24  	}
25  
26  	@Test
27  	public void testEdit_NoUniqueMiddleSide_FlipBlocks() {
28  		EditList r = diff(t("aRRSSz"), t("aSSRRz"));
29  		assertEquals(2, r.size());
30  		assertEquals(new Edit(1, 3, 1, 1), r.get(0)); // DELETE "RR"
31  		assertEquals(new Edit(5, 5, 3, 5), r.get(1)); // INSERT "RR
32  	}
33  
34  	@Test
35  	public void testEdit_NoUniqueMiddleSide_Insert2() {
36  		EditList r = diff(t("aRSz"), t("aRRSSz"));
37  		assertEquals(1, r.size());
38  		assertEquals(new Edit(2, 2, 2, 4), r.get(0));
39  	}
40  
41  	@Test
42  	public void testEdit_NoUniqueMiddleSide_FlipAndExpand() {
43  		EditList r = diff(t("aRSz"), t("aSSRRz"));
44  		assertEquals(2, r.size());
45  		assertEquals(new Edit(1, 2, 1, 1), r.get(0)); // DELETE "R"
46  		assertEquals(new Edit(3, 3, 2, 5), r.get(1)); // INSERT "SRR"
47  	}
48  
49  	@Test
50  	public void testEdit_LcsContainsUnique() {
51  		EditList r = diff(t("nqnjrnjsnm"), t("AnqnjrnjsnjTnmZ"));
52  		assertEquals(new Edit(0, 0, 0, 1), r.get(0)); // INSERT "A";
53  		assertEquals(new Edit(9, 9, 10, 13), r.get(1)); // INSERT "jTn";
54  		assertEquals(new Edit(10, 10, 14, 15), r.get(2)); // INSERT "Z";
55  		assertEquals(3, r.size());
56  	}
57  
58  	@Test
59  	public void testExceedsChainLength_DuringScanOfA() {
60  		HistogramDiff hd = new HistogramDiff();
61  		hd.setFallbackAlgorithm(null);
62  		hd.setMaxChainLength(3);
63  
64  		SequenceComparator<RawText> cmp = new SequenceComparator<RawText>() {
65  			@Override
66  			public boolean equals(RawText a, int ai, RawText b, int bi) {
67  				return RawTextComparator.DEFAULT.equals(a, ai, b, bi);
68  			}
69  
70  			@Override
71  			public int hash(RawText a, int ai) {
72  				return 1;
73  			}
74  		};
75  
76  		EditList r = hd.diff(cmp, t("RabS"), t("QabT"));
77  		assertEquals(1, r.size());
78  		assertEquals(new Edit(0, 4, 0, 4), r.get(0));
79  	}
80  
81  	@Test
82  	public void testExceedsChainLength_DuringScanOfB() {
83  		HistogramDiff hd = new HistogramDiff();
84  		hd.setFallbackAlgorithm(null);
85  		hd.setMaxChainLength(1);
86  
87  		EditList r = hd.diff(RawTextComparator.DEFAULT, t("RaaS"), t("QaaT"));
88  		assertEquals(1, r.size());
89  		assertEquals(new Edit(0, 4, 0, 4), r.get(0));
90  	}
91  
92  	@Test
93  	public void testFallbackToMyersDiff() {
94  		HistogramDiff hd = new HistogramDiff();
95  		hd.setMaxChainLength(4);
96  
97  		RawTextComparator cmp = RawTextComparator.DEFAULT;
98  		RawText ac = t("bbbbb");
99  		RawText bc = t("AbCbDbEFbZ");
100 		EditList r;
101 
102 		// Without fallback our results are limited due to collisions.
103 		hd.setFallbackAlgorithm(null);
104 		r = hd.diff(cmp, ac, bc);
105 		assertEquals(1, r.size());
106 
107 		// Results go up when we add a fallback for the high collision regions.
108 		hd.setFallbackAlgorithm(MyersDiff.INSTANCE);
109 		r = hd.diff(cmp, ac, bc);
110 		assertEquals(5, r.size());
111 	}
112 }