Assert that certain parameterized vectors will throw an exception in JUnit?

Question

I wonder how I can write test for particular exception assertion?

For example (my test data container):

@Parameters(name = "{index}: {0} > {1} > {2} > {3} > {4}")
public static Iterable<Object[]> data() {
  return Arrays.asList(new Object[][] {
    {"1200", new byte[] {0x4B0}, "1200", 16, 2},
    {"10", new byte[] {0x0A}, "10", 8, 1},
    {"13544k0", new byte[] {0x0A}, "1200", 8, 1},  <== assert thrown exception
    {"132111115516", new byte[] {0x0A}, "1200", 8, 1},<== assert thrown exception
  });
}

Is it possible to use such container data to assert exception, or I need to model situation in concrete test-method?

Answer 1

Before JUnit 4.7, it wasn't possible to use data-driven testing like this, where some data combinations produce exceptions and some don't.

It is possible to create two different data-driven tests, where all the combinations in one don't produce exceptions, and all the combinations in the other do produce exceptions.

Use the @Test(expected=YourException.class) for the tests that expect exceptions, unless you need extra test logic. The expected annotation parameter isn't very powerful.

Since 4.7, there's been an @Rule that works for it. See @eee's answer for details.

Answer 2

You can use the JUnit rule ExpectedException for this, here is a runnable example:

@RunWith(Parameterized.class)
public class MyParameterizedTest {

    public class UnderTest {
        public void execute(String input) {
            if ("1".equals(input)) {
                throw new RuntimeException();
            }
        }
    }

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

    @Parameters(name = "{index}: {0}")
    public static Iterable<Object[]> data() {
        return Arrays.asList(new Object[][] {
                    {"1", RuntimeException.class},
                    {"2", null}    
        });
    }

    @Parameter(value = 0)
    public String input;

    @Parameter(value = 1)
    public Class<Throwable> exceptionClass;

    @Test
    public void test() {
        if (exceptionClass != null) {
            expected.expect(exceptionClass);
        }

        UnderTest underTest = new UnderTest();          
        underTest.execute(input);
    }
}