解读Junit的@Test注解，避免initializationerror

青旅半醒 2022-06-13 01:14 217阅读 0赞

##### ![Open Declaration][]org.junit.Test #####

@Target(value=\{ METHOD\}) \- - - target注解：有效目标--只作用于方法  
@Retention(value=RUNTIME) \- - - Retention注解：有效范围--运行时

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.

（test注解告诉Junit为要做测试的public权限的方法创建一个测试实例。为了运行这个方法，Junit首先会创建一个该类实例，用于调用被@Test注解了的方法。遇到任何异常抛出时，Junit都会执行失败。如果没有异常抛出，Junit测试必然会成功）

A simple test looks like this:  （简单实例如下：）

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.

（test注解可支持两个可选参数。第一个参数为：excepted----声明被测试方法应该抛出的异常。如果没有抛出异常或抛出的异常不是声明的异常，则会测试失败。）

For example, the following test succeeds: （比如，下面的成功测试：）

@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`ExpectedException` rule can be used. Further information about exception testing can be found at the[JUnit Wiki][].

（如果要验证异常信息或某个属性，可是使用`ExpectedException的规则（即在这种情况下推荐使用Exception参数）。若要了解exception测试的详细信息可以去JUnit Wiki 中查看。）`

The second optional parameter, `timeout`, causes a test to fail if it takes longer than a specified amount of clock time (measured in milliseconds).

（第二个可选参数：timeout--如果单元测试的实际超过了规定的时间，则会显示测试失败。单位：毫秒）

The following test fails: （如下，测试失败情况：）

@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:

（警告：尽管timeout对于捕获和终止无限循环体非常有用，但应该考虑其不确定性。下面的测试可能会或可能不会失败，这个要根据运行系统的线程决定。）

@Test(timeout=100) public void sleep100() {
           Thread.sleep(100);
        }

**T****HREAD 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 `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

（线程安全性警告：@Test方法的参数timeout只作用于一个线程上，除了运行时固定会执行的@Before和@After 方法的线程。。。。。）

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@Test注解：只能作用于public权限的方法

[Open Declaration]: 
[JUnit Wiki]: https://github.com/junit-team/junit/wiki/Exception-testing