KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > junit > ComparisonFailure


1 package org.junit;
2
3 /**
4  * Thrown when an {@link org.junit.Assert#assertEquals(Object, Object) assertEquals(String, String)} fails. Create and throw
5  * a <code>ComparisonFailure</code> manually if you want to show users the difference between two complex
6  * strings.
7  *
8  * Inspired by a patch from Alex Chaffee (alex@purpletech.com)
9  */
10 public class ComparisonFailure extends AssertionError JavaDoc {
11     /**
12      * The maximum length for fExpected and fActual. If it is exceeded, the strings should be shortened.
13      * @see ComparisonCompactor
14      */
15     private static final int MAX_CONTEXT_LENGTH= 20;
16     private static final long serialVersionUID= 1L;
17     
18     private String JavaDoc fExpected;
19     private String JavaDoc fActual;
20
21     /**
22      * Constructs a comparison failure.
23      * @param message the identifying message or null
24      * @param expected the expected string value
25      * @param actual the actual string value
26      */
27     public ComparisonFailure (String JavaDoc message, String JavaDoc expected, String JavaDoc actual) {
28         super (message);
29         fExpected= expected;
30         fActual= actual;
31     }
32     
33     /**
34      * Returns "..." in place of common prefix and "..." in
35      * place of common suffix between expected and actual.
36      *
37      * @see Throwable#getMessage()
38      */
39     @Override JavaDoc
40     public String JavaDoc getMessage() {
41         return new ComparisonCompactor(MAX_CONTEXT_LENGTH, fExpected, fActual).compact(super.getMessage());
42     }
43     
44     /**
45      * Returns the actual string value
46      * @return the actual string value
47      */
48     public String JavaDoc getActual() {
49         return fActual;
50     }
51     /**
52      * Returns the expected string value
53      * @return the expected string value
54      */
55     public String JavaDoc getExpected() {
56         return fExpected;
57     }
58     
59     private static class ComparisonCompactor {
60         private static final String JavaDoc ELLIPSIS= "...";
61         private static final String JavaDoc DELTA_END= "]";
62         private static final String JavaDoc DELTA_START= "[";
63         
64         /**
65          * The maximum length for <code>expected</code> and <code>actual</code>. When <code>contextLength</code>
66          * is exceeded, the Strings are shortened
67          */
68         private int fContextLength;
69         private String JavaDoc fExpected;
70         private String JavaDoc fActual;
71         private int fPrefix;
72         private int fSuffix;
73
74         /**
75          * @param contextLength the maximum length for <code>expected</code> and <code>actual</code>. When contextLength
76          * is exceeded, the Strings are shortened
77          * @param expected the expected string value
78          * @param actual the actual string value
79          */
80         public ComparisonCompactor(int contextLength, String JavaDoc expected, String JavaDoc actual) {
81             fContextLength= contextLength;
82             fExpected= expected;
83             fActual= actual;
84         }
85
86         public String JavaDoc compact(String JavaDoc message) {
87             if (fExpected == null || fActual == null || areStringsEqual())
88                 return Assert.format(message, fExpected, fActual);
89
90             findCommonPrefix();
91             findCommonSuffix();
92             String JavaDoc expected= compactString(fExpected);
93             String JavaDoc actual= compactString(fActual);
94             return Assert.format(message, expected, actual);
95         }
96
97         private String JavaDoc compactString(String JavaDoc source) {
98             String JavaDoc result= DELTA_START + source.substring(fPrefix, source.length() - fSuffix + 1) + DELTA_END;
99             if (fPrefix > 0)
100                 result= computeCommonPrefix() + result;
101             if (fSuffix > 0)
102                 result= result + computeCommonSuffix();
103             return result;
104         }
105
106         private void findCommonPrefix() {
107             fPrefix= 0;
108             int end= Math.min(fExpected.length(), fActual.length());
109             for (; fPrefix < end; fPrefix++) {
110                 if (fExpected.charAt(fPrefix) != fActual.charAt(fPrefix))
111                     break;
112             }
113         }
114
115         private void findCommonSuffix() {
116             int expectedSuffix= fExpected.length() - 1;
117             int actualSuffix= fActual.length() - 1;
118             for (; actualSuffix >= fPrefix && expectedSuffix >= fPrefix; actualSuffix--, expectedSuffix--) {
119                 if (fExpected.charAt(expectedSuffix) != fActual.charAt(actualSuffix))
120                     break;
121             }
122             fSuffix= fExpected.length() - expectedSuffix;
123         }
124
125         private String JavaDoc computeCommonPrefix() {
126             return (fPrefix > fContextLength ? ELLIPSIS : "") + fExpected.substring(Math.max(0, fPrefix - fContextLength), fPrefix);
127         }
128
129         private String JavaDoc computeCommonSuffix() {
130             int end= Math.min(fExpected.length() - fSuffix + 1 + fContextLength, fExpected.length());
131             return fExpected.substring(fExpected.length() - fSuffix + 1, end) + (fExpected.length() - fSuffix + 1 < fExpected.length() - fContextLength ? ELLIPSIS : "");
132         }
133
134         private boolean areStringsEqual() {
135             return fExpected.equals(fActual);
136         }
137     }
138 }
Popular Tags