如何编写自定义JUnit断言的测试？

Question

比方说，我创建了我自己的assertSomething(...)方法。我如何编写单元测试来验证它是否正确地使测试用例失败？

Answer 1

您应该看看Junit 4.7中引入的规则。特别是TestWatcher。

TestWatcher是规则的基类，它记录了测试操作，但未对其进行修改。例如，这个类将保持每个通过和未通过测试的日志：

public static class WatchmanTest { 
    private static String watchedLog; 

    @Rule 
    public TestWatcher watchman= new TestWatcher() { 
    @Override 
    protected void failed(Throwable e, Description description) { 
     watchedLog+= description + "\n"; 
    } 

    @Override 
    protected void succeeded(Description description) { 
     watchedLog+= description + " " + "success!\n"; 
    } 
    }; 

    @Test 
    public void fails() { 
    fail(); 
    } 

    @Test 
    public void succeeds() { 
    } 
} 

Answer 2

如果我理解正确，我看到了未来的方式：

@Test 
public void assertSomethingSuccessTest() { 
    // given 
    final Object givenActualResult = new Object(); // put your objects here 
    final Object givenExpectedResult = new Object(); // put your objects here 

    // when 
    assertSomething(givenActualResult, givenExpectedResult); 

    // then 
    // no exception is expected here 
} 

// TODO: specify exactly your exception here if any 
@Test(expected = RuntimeException.class) 
public void assertSomethingFailedTest() { 
    // given 
    final Object givenActualResult = new Object(); // put your objects here 
    final Object givenExpectedResult = new Object(); // put your objects here 

    // when 
    assertSomething(givenActualResult, givenExpectedResult); 

    // then 
    // an exception is expected here, see annotated expected exception. 
} 

如果您需要验证异常以及：

@Rule 
public ExpectedException thrown = ExpectedException.none(); 

@Test 
public void assertSomethingFailedTest() { 
    // given 
    final Object givenActualResult = new Object(); // put your objects here 
    final Object givenExpectedResult = new Object(); // put your objects here 

    // and 
    thrown.expect(RuntimeException.class); 
    thrown.expectMessage("happened?"); 

    // when 
    assertSomething(givenActualResult, givenExpectedResult); 

    // then 
    // an exception is expected here, see configured ExpectedException rule. 
}