001 package org.junit;
002
003 import static java.util.Arrays.asList;
004 import static org.hamcrest.CoreMatchers.everyItem;
005 import static org.hamcrest.CoreMatchers.is;
006 import static org.hamcrest.CoreMatchers.notNullValue;
007 import static org.hamcrest.CoreMatchers.nullValue;
008
009 import org.hamcrest.Matcher;
010
011 /**
012 * A set of methods useful for stating assumptions about the conditions in which a test is meaningful.
013 * A failed assumption does not mean the code is broken, but that the test provides no useful information. Assume
014 * basically means "don't run this test if these conditions don't apply". The default JUnit runner skips tests with
015 * failing assumptions. Custom runners may behave differently.
016 * <p>
017 * A good example of using assumptions is in <a href="https://github.com/junit-team/junit4/wiki/Theories">Theories</a> where they are needed to exclude certain datapoints that aren't suitable or allowed for a certain test case.
018 * </p>
019 * Failed assumptions are usually not logged, because there may be many tests that don't apply to certain
020 * configurations.
021 *
022 * <p>
023 * These methods can be used directly: <code>Assume.assumeTrue(...)</code>, however, they
024 * read better if they are referenced through static import:<br/>
025 * <pre>
026 * import static org.junit.Assume.*;
027 * ...
028 * assumeTrue(...);
029 * </pre>
030 * </p>
031 *
032 * @see <a href="https://github.com/junit-team/junit4/wiki/Theories">Theories</a>
033 *
034 * @since 4.4
035 */
036 public class Assume {
037 /**
038 * If called with an expression evaluating to {@code false}, the test will halt and be ignored.
039 */
040 public static void assumeTrue(boolean b) {
041 assumeThat(b, is(true));
042 }
043
044 /**
045 * The inverse of {@link #assumeTrue(boolean)}.
046 */
047 public static void assumeFalse(boolean b) {
048 assumeTrue(!b);
049 }
050
051 /**
052 * If called with an expression evaluating to {@code false}, the test will halt and be ignored.
053 *
054 * @param b If <code>false</code>, the method will attempt to stop the test and ignore it by
055 * throwing {@link AssumptionViolatedException}.
056 * @param message A message to pass to {@link AssumptionViolatedException}.
057 */
058 public static void assumeTrue(String message, boolean b) {
059 if (!b) throw new AssumptionViolatedException(message);
060 }
061
062 /**
063 * The inverse of {@link #assumeTrue(String, boolean)}.
064 */
065 public static void assumeFalse(String message, boolean b) {
066 assumeTrue(message, !b);
067 }
068
069 /**
070 * If called with one or more null elements in <code>objects</code>, the test will halt and be ignored.
071 */
072 public static void assumeNotNull(Object... objects) {
073 assumeThat(asList(objects), everyItem(notNullValue()));
074 }
075
076 /**
077 * Call to assume that <code>actual</code> satisfies the condition specified by <code>matcher</code>.
078 * If not, the test halts and is ignored.
079 * Example:
080 * <pre>:
081 * assumeThat(1, is(1)); // passes
082 * foo(); // will execute
083 * assumeThat(0, is(1)); // assumption failure! test halts
084 * int x = 1 / 0; // will never execute
085 * </pre>
086 *
087 * @param <T> the static type accepted by the matcher (this can flag obvious compile-time problems such as {@code assumeThat(1, is("a"))}
088 * @param actual the computed value being compared
089 * @param matcher an expression, built of {@link Matcher}s, specifying allowed values
090 * @see org.hamcrest.CoreMatchers
091 * @see org.junit.matchers.JUnitMatchers
092 */
093 public static <T> void assumeThat(T actual, Matcher<T> matcher) {
094 if (!matcher.matches(actual)) {
095 throw new AssumptionViolatedException(actual, matcher);
096 }
097 }
098
099 /**
100 * Call to assume that <code>actual</code> satisfies the condition specified by <code>matcher</code>.
101 * If not, the test halts and is ignored.
102 * Example:
103 * <pre>:
104 * assumeThat("alwaysPasses", 1, is(1)); // passes
105 * foo(); // will execute
106 * assumeThat("alwaysFails", 0, is(1)); // assumption failure! test halts
107 * int x = 1 / 0; // will never execute
108 * </pre>
109 *
110 * @param <T> the static type accepted by the matcher (this can flag obvious compile-time problems such as {@code assumeThat(1, is("a"))}
111 * @param actual the computed value being compared
112 * @param matcher an expression, built of {@link Matcher}s, specifying allowed values
113 * @see org.hamcrest.CoreMatchers
114 * @see org.junit.matchers.JUnitMatchers
115 */
116 public static <T> void assumeThat(String message, T actual, Matcher<T> matcher) {
117 if (!matcher.matches(actual)) {
118 throw new AssumptionViolatedException(message, actual, matcher);
119 }
120 }
121
122 /**
123 * Use to assume that an operation completes normally. If {@code e} is non-null, the test will halt and be ignored.
124 *
125 * For example:
126 * <pre>
127 * \@Test public void parseDataFile() {
128 * DataFile file;
129 * try {
130 * file = DataFile.open("sampledata.txt");
131 * } catch (IOException e) {
132 * // stop test and ignore if data can't be opened
133 * assumeNoException(e);
134 * }
135 * // ...
136 * }
137 * </pre>
138 *
139 * @param e if non-null, the offending exception
140 */
141 public static void assumeNoException(Throwable e) {
142 assumeThat(e, nullValue());
143 }
144
145 /**
146 * Attempts to halt the test and ignore it if Throwable <code>e</code> is
147 * not <code>null</code>. Similar to {@link #assumeNoException(Throwable)},
148 * but provides an additional message that can explain the details
149 * concerning the assumption.
150 *
151 * @param e if non-null, the offending exception
152 * @param message Additional message to pass to {@link AssumptionViolatedException}.
153 * @see #assumeNoException(Throwable)
154 */
155 public static void assumeNoException(String message, Throwable e) {
156 assumeThat(message, e, nullValue());
157 }
158 }