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JUnit is a unit testing framework for Java, created by Erich Gamma and Kent Beck.
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package org.junit;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * The Test annotation tells JUnit that the public void method
 * to which it is attached can be run as a test case. To run the method,
 * JUnit first constructs a fresh instance of the class then invokes the
 * annotated method. Any exceptions thrown by the test will be reported
 * by JUnit as a failure. If no exceptions are thrown, the test is assumed
 * to have succeeded.
 * 
 * A simple test looks like this:
 * 
 * public class Example {
 *    @Test
 *    public void method() {
 *       org.junit.Assert.assertTrue( new ArrayList().isEmpty() );
 *    }
 * }
 * 
 * 
 * The Test annotation supports two optional parameters.
 * The first, expected, declares that a test method should throw
 * an exception. If it doesn't throw an exception or if it throws a different exception
 * than the one declared, the test fails. For example, the following test succeeds:
 * 
 *    @Test(expected=IndexOutOfBoundsException.class) public void outOfBounds() {
 *       new ArrayList<Object>().get(1);
 *    }
 * 
 * If the exception's message or one of its properties should be verified, the
 * {@link org.junit.rules.ExpectedException ExpectedException} rule can be used. Further
 * information about exception testing can be found at the
 * JUnit Wiki.
 * 
 * The second optional parameter, timeout, causes a test to fail if it takes
 * longer than a specified amount of clock time (measured in milliseconds). The following test fails:
 * 
 *    @Test(timeout=100) public void infinity() {
 *       while(true);
 *    }
 * 
 * Warning: while timeout is useful to catch and terminate
 * infinite loops, it should not be considered deterministic. The
 * following test may or may not fail depending on how the operating system
 * schedules threads:
 *  *    @Test(timeout=100) public void sleep100() {
 *       Thread.sleep(100);
 *    }
 * 
 * THREAD SAFETY WARNING: Test methods with a timeout parameter are run in a thread other than the
 * thread which runs the fixture's @Before and @After methods. This may yield different behavior for
 * code that is not thread safe when compared to the same test method without a timeout parameter.
 * Consider using the {@link org.junit.rules.Timeout} rule instead, which ensures a test method is run on the
 * same thread as the fixture's @Before and @After methods.
 *
 * @since 4.0
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface Test {

    /**
     * Default empty exception
     */
    static class None extends Throwable {
        private static final long serialVersionUID = 1L;

        private None() {
        }
    }

    /**
     * Optionally specify expected, a Throwable, to cause a test method to succeed if
     * and only if an exception of the specified class is thrown by the method. If the Throwable's
     * message or one of its properties should be verified, the
     * {@link org.junit.rules.ExpectedException ExpectedException} rule can be used instead.
     */
    Class expected() default None.class;

    /**
     * Optionally specify timeout in milliseconds to cause a test method to fail if it
     * takes longer than that number of milliseconds.
     * 
     * THREAD SAFETY WARNING: Test methods with a timeout parameter are run in a thread other than the
     * thread which runs the fixture's @Before and @After methods. This may yield different behavior for
     * code that is not thread safe when compared to the same test method without a timeout parameter.
     * Consider using the {@link org.junit.rules.Timeout} rule instead, which ensures a test method is run on the
     * same thread as the fixture's @Before and @After methods.
     * 
     */
    long timeout() default 0L;
}