001 package org.junit;
002
003 import java.lang.annotation.ElementType;
004 import java.lang.annotation.Retention;
005 import java.lang.annotation.RetentionPolicy;
006 import java.lang.annotation.Target;
007
008 /**
009 * Annotates fields that reference rules or methods that return a rule. A field must be public, not
010 * static, and a subtype of {@link org.junit.rules.TestRule} (preferred) or
011 * {@link org.junit.rules.MethodRule}. A method must be public, not static,
012 * and must return a subtype of {@link org.junit.rules.TestRule} (preferred) or
013 * {@link org.junit.rules.MethodRule}.
014 * <p>
015 * The {@link org.junit.runners.model.Statement} passed
016 * to the {@link org.junit.rules.TestRule} will run any {@link Before} methods,
017 * then the {@link Test} method, and finally any {@link After} methods,
018 * throwing an exception if any of these fail. If there are multiple
019 * annotated {@link Rule}s on a class, they will be applied in order of methods first, then fields.
020 * However, if there are multiple fields (or methods) they will be applied in an order
021 * that depends on your JVM's implementation of the reflection API, which is
022 * undefined, in general. Rules defined by fields will always be applied
023 * after Rules defined by methods, i.e. the Statements returned by the former will
024 * be executed around those returned by the latter.
025 *
026 * <h3>Usage</h3>
027 * <p>
028 * For example, here is a test class that creates a temporary folder before
029 * each test method, and deletes it after each:
030 * <pre>
031 * public static class HasTempFolder {
032 * @Rule
033 * public TemporaryFolder folder= new TemporaryFolder();
034 *
035 * @Test
036 * public void testUsingTempFolder() throws IOException {
037 * File createdFile= folder.newFile("myfile.txt");
038 * File createdFolder= folder.newFolder("subfolder");
039 * // ...
040 * }
041 * }
042 * </pre>
043 * <p>
044 * And the same using a method.
045 * <pre>
046 * public static class HasTempFolder {
047 * private TemporaryFolder folder= new TemporaryFolder();
048 *
049 * @Rule
050 * public TemporaryFolder getFolder() {
051 * return folder;
052 * }
053 *
054 * @Test
055 * public void testUsingTempFolder() throws IOException {
056 * File createdFile= folder.newFile("myfile.txt");
057 * File createdFolder= folder.newFolder("subfolder");
058 * // ...
059 * }
060 * }
061 * </pre>
062 * <p>
063 * For more information and more examples, see
064 * {@link org.junit.rules.TestRule}.
065 *
066 * <h3>Ordering</h3>
067 * <p>
068 * You can use {@link #order()} if you want to have control over the order in
069 * which the Rules are applied.
070 *
071 * <pre>
072 * public class ThreeRules {
073 * @Rule(order = 0)
074 * public LoggingRule outer = new LoggingRule("outer rule");
075 *
076 * @Rule(order = 1)
077 * public LoggingRule middle = new LoggingRule("middle rule");
078 *
079 * @Rule(order = 2)
080 * public LoggingRule inner = new LoggingRule("inner rule");
081 *
082 * // ...
083 * }
084 * </pre>
085 *
086 * @since 4.7
087 */
088 @Retention(RetentionPolicy.RUNTIME)
089 @Target({ElementType.FIELD, ElementType.METHOD})
090 public @interface Rule {
091
092 int DEFAULT_ORDER = -1;
093
094 /**
095 * Specifies the order in which rules are applied. The rules with a higher value are inner.
096 *
097 * @since 4.13
098 */
099 int order() default DEFAULT_ORDER;
100
101 }