src/main/java/org/junit/rules/MethodRule.java


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package org.junit.rules;

import org.junit.Rule;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.Statement;

/**
 * A MethodRule is an alteration in how a test method is run and reported.
 * Multiple {@link MethodRule}s can be applied to a test method. The
 * {@link Statement} that executes the method is passed to each annotated
 * {@link Rule} in turn, and each may return a substitute or modified
 * {@link Statement}, which is passed to the next {@link Rule}, if any. For
 * examples of how this can be useful, see these provided MethodRules,
 * or write your own:
 *
 * <ul>
 *   <li>{@link ErrorCollector}: collect multiple errors in one test method</li>
 *   <li>{@link ExpectedException}: make flexible assertions about thrown exceptions</li>
 *   <li>{@link ExternalResource}: start and stop a server, for example</li>
 *   <li>{@link TemporaryFolder}: create fresh files, and delete after test</li>
 *   <li>{@link TestName}: remember the test name for use during the method</li>
 *   <li>{@link TestWatchman}: add logic at events during method execution</li>
 *   <li>{@link Timeout}: cause test to fail after a set time</li>
 *   <li>{@link Verifier}: fail test if object state ends up incorrect</li>
 * </ul>
 *
 * Note that {@link MethodRule} has been replaced by {@link TestRule},
 * which has the added benefit of supporting class rules.
 *
 * @since 4.7
 */
public interface MethodRule {
    /**
     * Modifies the method-running {@link Statement} to implement an additional
     * test-running rule.
     *
     * @param base The {@link Statement} to be modified
     * @param method The method to be run
     * @param target The object on which the method will be run.
     * @return a new statement, which may be the same as {@code base},
     *         a wrapper around {@code base}, or a completely new Statement.
     */
    Statement apply(Statement base, FrameworkMethod method, Object target);
}