001package org.junit.rules;
002
003import org.junit.Rule;
004import org.junit.runners.model.FrameworkMethod;
005import org.junit.runners.model.Statement;
006
007/**
008 * A MethodRule is an alteration in how a test method is run and reported.
009 * Multiple {@link MethodRule}s can be applied to a test method. The
010 * {@link Statement} that executes the method is passed to each annotated
011 * {@link Rule} in turn, and each may return a substitute or modified
012 * {@link Statement}, which is passed to the next {@link Rule}, if any. For
013 * examples of how this can be useful, see these provided MethodRules,
014 * or write your own:
015 *
016 * <ul>
017 *   <li>{@link ErrorCollector}: collect multiple errors in one test method</li>
018 *   <li>{@link ExpectedException}: make flexible assertions about thrown exceptions</li>
019 *   <li>{@link ExternalResource}: start and stop a server, for example</li>
020 *   <li>{@link TemporaryFolder}: create fresh files, and delete after test</li>
021 *   <li>{@link TestName}: remember the test name for use during the method</li>
022 *   <li>{@link TestWatchman}: add logic at events during method execution</li>
023 *   <li>{@link Timeout}: cause test to fail after a set time</li>
024 *   <li>{@link Verifier}: fail test if object state ends up incorrect</li>
025 * </ul>
026 *
027 * Note that {@link MethodRule} has been replaced by {@link TestRule},
028 * which has the added benefit of supporting class rules.
029 *
030 * @since 4.7
031 */
032public interface MethodRule {
033    /**
034     * Modifies the method-running {@link Statement} to implement an additional
035     * test-running rule.
036     *
037     * @param base The {@link Statement} to be modified
038     * @param method The method to be run
039     * @param target The object on with the method will be run.
040     * @return a new statement, which may be the same as {@code base},
041     *         a wrapper around {@code base}, or a completely new Statement.
042     */
043    Statement apply(Statement base, FrameworkMethod method, Object target);
044}