如何使用ExpectedException规则在一个测试中测试多个异常？

Question

对junit的ExpectedException规则的使用有疑问:

正如这里建议的那样:junit ExpectedException 从junit 4.7开始的规则可以测试这样的异常(这比@Test(expected = Exception.class)要好得多):

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

@Test
public void testFailuresOfClass() {
 Foo foo = new Foo();
 exception.expect(Exception.class);
 foo.doStuff();
}

现在我需要在一个测试方法中测试几个异常,并在运行以下测试后得到一个绿色条,因此认为每个测试都通过了.

@Test
public void testFailuresOfClass() {
 Foo foo = new Foo();

 exception.expect(IndexOutOfBoundsException.class);
 foo.doStuff();

 //this is not tested anymore and if the first passes everything looks fine
 exception.expect(NullPointerException.class);
 foo.doStuff(null);

 exception.expect(MyOwnException.class);
 foo.doStuff(null,"");

 exception.expect(DomainException.class);
 foo.doOtherStuff();
}

但是过了一会儿,我意识到第一次检查通过后,测试方法就会退出.至少可以说这是模棱两可的.在junit 3中这很容易实现......所以这是我的问题:

如何使用ExpectedException规则在一个测试中测试多个异常？

Answer 1

简答:你做不到.

如果第一次打电话 - foo.doStuff()抛出异常,你永远不会到达foo.doStuff(null).你必须将你的测试分成几个(对于这个简单的情况,我建议回到简单的符号,没有ExpectedException):

private Foo foo;

@Before 
public void setUp() {
 foo = new Foo();
}

@Test(expected = IndexOutOfBoundsException.class)
public void noArgsShouldFail() {
 foo.doStuff();
}

@Test(expected = NullPointerException.class)
public void nullArgShouldFail() {
 foo.doStuff(null);
}

@Test(expected = MyOwnException.class)
public void nullAndEmptyStringShouldFail() {
 foo.doStuff(null,"");
}

@Test(expected = DomainException.class)
public void doOtherStuffShouldFail() {
 foo.doOtherStuff();
}

如果你真的想要一个且只有一个测试,那么你可以fail在没有错误的情况下抛出错误,并抓住你期望的东西:

@Test
public void testFailuresOfClass() {
 Foo foo = new Foo();

 try {
    foo.doStuff();
    fail("doStuff() should not have succeeded");
 } catch (IndexOutOfBoundsException expected) {
    // This is what we want.
 }
 try {
    foo.doStuff(null);
    fail("doStuff(null) should not have succeeded");
 } catch (NullPointerException expected) {
    // This is what we want.
 }
 // etc for other failure modes
}

但是,这很快就会变得非常混乱,如果第一个期望失败,你将看不到其他任何事情也会失败,这在排除故障时会很烦人.