Java 8解决方案

Question

在JUnit中，我目前正在使用注释来测试我的测试中的异常。

有没有办法分析这个例外？例如，我希望CriticalServerException，但我也想验证getMessage方法的内容。

Answer 1

如果您有 JUnit 4.7 或以上，请尝试ExpectedException

this question中有一个示例，复制如下：

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

@Test
public void testRodneCisloRok(){
    exception.expect(IllegalArgumentException.class);
    exception.expectMessage("error1");
    new RodneCislo("891415",dopocitej("891415"));
}

Answer 2

我不确定你是否应该这样做。使用try-catch块检查错误消息是 junit3ish 。我们现在有这个很酷的功能，您可以编写@Test(expected=CriticalServerException.class)并且想要“返回”并再次使用try-catch来获取您期望的异常，只是为了检查错误消息？

IMO你应该留下@Test(expected=CriticalServerException.class)注释并忽略错误信息。检查错误消息，可以更改，因为它是一个更“人类可读”的字符串而不是技术值，也可能是棘手的。您强制异常有特定的错误消息，但您可能不知道是谁生成了异常以及他选择了什么错误消息。

通常，您希望测试方法是否抛出异常，而不是实际的错误消息。如果错误消息非常重要，您应该考虑使用它抛出的异常的子类，并在@Test(expected=...)中进行检查。

Answer 3

try{ 
    //your code expecting to throw an exception
    fail("Failed to assert :No exception thrown");
} catch(CriticalServerException ex){
    assertNotNull("Failed to assert", ex.getMessage()) 
    assertEquals("Failed to assert", "Expected Message", ex.getMessage());
}

Answer 4

try
{
    // your code

    fail("Didn't throw expected exception");
}
catch(CriticalServerException e)
{
    assertEquals("Expected message", e.getMessage());
}

Answer 5

try {
    // test code invacation
    fail("Exception not throw!!!");
} catch(CriticalServerException ex) {
    assertTrue("Invalid exception data", ex.toString().contains("error text"));
}

Answer 6

如果要测试的测试用例很多，请使用 MethodRule 作为常用解决方案

public class ExceptionRule implements MethodRule {
    @Override
    public Statement apply(final Statement base, final FrameworkMethod method, Object target) {
        return new Statement() {
            @Override
            public void evaluate() throws Throwable {
                try {
                    base.evaluate();
                    Assert.fail();
                } catch (CriticalServerException e) {
                    //Analyze the exception here
                }
            }
        };    
    }
}

然后将规则用于您的测试类：

@Rule public ExceptionRule rule = new ExceptionRule();

Answer 7

我认为没有办法使用注释来做到这一点。你可能不得不回到try-catch方式，在catch块中你可以验证消息

Answer 8

使用catch-exception：

catchException(obj).doSomethingCritical();
assertTrue(caughtException() instanceof CriticalServerException);
assertEquals("Expected Message", caughtException().getMessage());

Answer 9

看看fluent-exception-rule，它“结合了Junit ExpectedException规则和AssertJ的断言方便性。”

import pl.wkr.fluentrule.api.FluentExpectedException;
...
@Rule
public FluentExpectedException thrown = FluentExpectedException.none();

@Test
public void testDoSomethingCritical() {
    thrown.expect(CriticalServerException.class).hasMessage("Expected Message").hasNoCause();
    obj.doSomethingCritical();
}

Answer 10

如果您想将消息与异常类型进行比较，那么您可以尝试下面的代码段。

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

    expectedException.expect(IllegalArgumentException.class);
    expectedException.expectMessage("Parameter is not valid"); //check string contains
    expectedException.expectMessage(CoreMatchers.equalTo("Parameter is not valid")); //check string equals

注意：这适用于junit 4.9以后。

Answer 11

Java 8解决方案

这是我写的实用函数：

public final <T extends Throwable> T expectException( Class<T> exceptionClass, Runnable runnable )
{
    try
    {
        runnable.run();
    }
    catch( Throwable throwable )
    {
        if( throwable instanceof AssertionError && throwable.getCause() != null )
            throwable = throwable.getCause(); //allows "assert x != null : new IllegalArgumentException();"
        assert exceptionClass.isInstance( throwable ) : throwable; //exception of the wrong kind was thrown.
        assert throwable.getClass() == exceptionClass : throwable; //exception thrown was a subclass, but not the exact class, expected.
        @SuppressWarnings( "unchecked" )
        T result = (T)throwable;
        return result;
    }
    assert false; //expected exception was not thrown.
    return null; //to keep the compiler happy.
}

（taken from my blog）

按如下方式使用：

@Test
public void testThrows()
{
    RuntimeException e = expectException( RuntimeException.class, () -> 
        {
            throw new RuntimeException( "fail!" );
        } );
    assert e.getMessage().equals( "fail!" );
}

此外，如果您想了解为什么想查看您的例外消息，请参阅：https://softwareengineering.stackexchange.com/a/278958/41811

JUnit测试 - 分析预期的异常

11 个答案:

Java 8解决方案