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 /**
039 * Do not instantiate.
040 * @deprecated since 4.13.
041 */
042 @Deprecated
043 public Assume() {
044 }
045
046 /**
047 * If called with an expression evaluating to {@code false}, the test will halt and be ignored.
048 */
049 public static void assumeTrue(boolean b) {
050 assumeThat(b, is(true));
051 }
052
053 /**
054 * The inverse of {@link #assumeTrue(boolean)}.
055 */
056 public static void assumeFalse(boolean b) {
057 assumeThat(b, is(false));
058 }
059
060 /**
061 * If called with an expression evaluating to {@code false}, the test will halt and be ignored.
062 *
063 * @param b If <code>false</code>, the method will attempt to stop the test and ignore it by
064 * throwing {@link AssumptionViolatedException}.
065 * @param message A message to pass to {@link AssumptionViolatedException}.
066 */
067 public static void assumeTrue(String message, boolean b) {
068 if (!b) throw new AssumptionViolatedException(message);
069 }
070
071 /**
072 * The inverse of {@link #assumeTrue(String, boolean)}.
073 */
074 public static void assumeFalse(String message, boolean b) {
075 assumeTrue(message, !b);
076 }
077
078 /**
079 * If called with a {@code null} array or one or more {@code null} elements in {@code objects},
080 * the test will halt and be ignored.
081 */
082 public static void assumeNotNull(Object... objects) {
083 assumeThat(objects, notNullValue());
084 assumeThat(asList(objects), everyItem(notNullValue()));
085 }
086
087 /**
088 * Call to assume that <code>actual</code> satisfies the condition specified by <code>matcher</code>.
089 * If not, the test halts and is ignored.
090 * Example:
091 * <pre>:
092 * assumeThat(1, is(1)); // passes
093 * foo(); // will execute
094 * assumeThat(0, is(1)); // assumption failure! test halts
095 * int x = 1 / 0; // will never execute
096 * </pre>
097 *
098 * @param <T> the static type accepted by the matcher (this can flag obvious compile-time problems such as {@code assumeThat(1, is("a"))}
099 * @param actual the computed value being compared
100 * @param matcher an expression, built of {@link Matcher}s, specifying allowed values
101 * @see org.hamcrest.CoreMatchers
102 * @see org.junit.matchers.JUnitMatchers
103 */
104 public static <T> void assumeThat(T actual, Matcher<T> matcher) {
105 if (!matcher.matches(actual)) {
106 throw new AssumptionViolatedException(actual, matcher);
107 }
108 }
109
110 /**
111 * Call to assume that <code>actual</code> satisfies the condition specified by <code>matcher</code>.
112 * If not, the test halts and is ignored.
113 * Example:
114 * <pre>:
115 * assumeThat("alwaysPasses", 1, is(1)); // passes
116 * foo(); // will execute
117 * assumeThat("alwaysFails", 0, is(1)); // assumption failure! test halts
118 * int x = 1 / 0; // will never execute
119 * </pre>
120 *
121 * @param <T> the static type accepted by the matcher (this can flag obvious compile-time problems such as {@code assumeThat(1, is("a"))}
122 * @param actual the computed value being compared
123 * @param matcher an expression, built of {@link Matcher}s, specifying allowed values
124 * @see org.hamcrest.CoreMatchers
125 * @see org.junit.matchers.JUnitMatchers
126 */
127 public static <T> void assumeThat(String message, T actual, Matcher<T> matcher) {
128 if (!matcher.matches(actual)) {
129 throw new AssumptionViolatedException(message, actual, matcher);
130 }
131 }
132
133 /**
134 * Use to assume that an operation completes normally. If {@code e} is non-null, the test will halt and be ignored.
135 *
136 * For example:
137 * <pre>
138 * \@Test public void parseDataFile() {
139 * DataFile file;
140 * try {
141 * file = DataFile.open("sampledata.txt");
142 * } catch (IOException e) {
143 * // stop test and ignore if data can't be opened
144 * assumeNoException(e);
145 * }
146 * // ...
147 * }
148 * </pre>
149 *
150 * @param e if non-null, the offending exception
151 */
152 public static void assumeNoException(Throwable e) {
153 assumeThat(e, nullValue());
154 }
155
156 /**
157 * Attempts to halt the test and ignore it if Throwable <code>e</code> is
158 * not <code>null</code>. Similar to {@link #assumeNoException(Throwable)},
159 * but provides an additional message that can explain the details
160 * concerning the assumption.
161 *
162 * @param e if non-null, the offending exception
163 * @param message Additional message to pass to {@link AssumptionViolatedException}.
164 * @see #assumeNoException(Throwable)
165 */
166 public static void assumeNoException(String message, Throwable e) {
167 assumeThat(message, e, nullValue());
168 }
169 }