001package org.junit;
002
003import java.lang.annotation.ElementType;
004import java.lang.annotation.Retention;
005import java.lang.annotation.RetentionPolicy;
006import 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 fields first, then methods.
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 * before Rules defined by methods. You can use a {@link org.junit.rules.RuleChain} if you want
024 * to have control over the order in which the Rules are applied.
025 * <p>
026 * For example, here is a test class that creates a temporary folder before
027 * each test method, and deletes it after each:
028 * <pre>
029 * public static class HasTempFolder {
030 *     &#064;Rule
031 *     public TemporaryFolder folder= new TemporaryFolder();
032 *
033 *     &#064;Test
034 *     public void testUsingTempFolder() throws IOException {
035 *         File createdFile= folder.newFile(&quot;myfile.txt&quot;);
036 *         File createdFolder= folder.newFolder(&quot;subfolder&quot;);
037 *         // ...
038 *     }
039 * }
040 * </pre>
041 * <p>
042 * And the same using a method.
043 * <pre>
044 * public static class HasTempFolder {
045 *     private TemporaryFolder folder= new TemporaryFolder();
046 *
047 *     &#064;Rule
048 *     public TemporaryFolder getFolder() {
049 *         return folder;
050 *     }
051 *
052 *     &#064;Test
053 *     public void testUsingTempFolder() throws IOException {
054 *         File createdFile= folder.newFile(&quot;myfile.txt&quot;);
055 *         File createdFolder= folder.newFolder(&quot;subfolder&quot;);
056 *         // ...
057 *     }
058 * }
059 * </pre>
060 * <p>
061 * For more information and more examples, see
062 * {@link org.junit.rules.TestRule}.
063 *
064 * @since 4.7
065 */
066@Retention(RetentionPolicy.RUNTIME)
067@Target({ElementType.FIELD, ElementType.METHOD})
068public @interface Rule {
069
070}