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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<>() {
65  
66  			@Override
67  			public boolean equals(RawText a, int ai, RawText b, int bi) {
68  				return RawTextComparator.DEFAULT.equals(a, ai, b, bi);
69  			}
70  
71  			@Override
72  			public int hash(RawText a, int ai) {
73  				return 1;
74  			}
75  		};
76  
77  		EditList r = hd.diff(cmp, t("RabS"), t("QabT"));
78  		assertEquals(1, r.size());
79  		assertEquals(new Edit(0, 4, 0, 4), r.get(0));
80  	}
81  
82  	@Test
83  	public void testExceedsChainLength_DuringScanOfB() {
84  		HistogramDiff hd = new HistogramDiff();
85  		hd.setFallbackAlgorithm(null);
86  		hd.setMaxChainLength(1);
87  
88  		EditList r = hd.diff(RawTextComparator.DEFAULT, t("RaaS"), t("QaaT"));
89  		assertEquals(1, r.size());
90  		assertEquals(new Edit(0, 4, 0, 4), r.get(0));
91  	}
92  
93  	@Test
94  	public void testFallbackToMyersDiff() {
95  		HistogramDiff hd = new HistogramDiff();
96  		hd.setMaxChainLength(4);
97  
98  		RawTextComparator cmp = RawTextComparator.DEFAULT;
99  		RawText ac = t("bbbbb");
100 		RawText bc = t("AbCbDbEFbZ");
101 		EditList r;
102 
103 		// Without fallback our results are limited due to collisions.
104 		hd.setFallbackAlgorithm(null);
105 		r = hd.diff(cmp, ac, bc);
106 		assertEquals(1, r.size());
107 
108 		// Results go up when we add a fallback for the high collision regions.
109 		hd.setFallbackAlgorithm(MyersDiff.INSTANCE);
110 		r = hd.diff(cmp, ac, bc);
111 		assertEquals(5, r.size());
112 	}
113 }