如何对无效验证方法的两种情况进行单元测试？

Question

I am writing a void validate method like this one:

void validate(SomeObject someObject) {
    if (check someObject with constraints) {
        throw new SomeException();
    }
}

To unit test this method, I would like to test both legal and illegal input:

• for illegal input, I used (expected = SomeException.class)
• I am wondering how we could test the case when someObject is legal?

Answer 1

Legal in this case means that the validation completes without exceptions. To test it you just need to call validate.

@Test
public void testLegal() throws SomeException {
     validator.validate(/* some legal object*/);
}

This test will fail only if an exception is thrown during validation.

Answer 2

1st Test Case :

@Test
public void testOK() throws Exception {
    validate(someObject);
    // At Least 1 assertion
}

2nd Test Case :

@Test(expected=SomeException.class)
public void testException() throws Exception {
    try {
        validate(someObject);
    } catch(SomeException e) {
        // At Least 1 assertion
        throw e;
    }
}

In this 2nd test case, if the exception is not thrown, the test will fail because it expects SommeException.class.

At least 1 assertion is mandatory because you must verify that the exception that has been thrown is well the one you were expected.

Answer 3

To test the case where someObject is legal, just call validate in a try block. If an exception is thrown, fail the test. If no exception is thrown, let the test end normally and pass, since that is the expected behavior.

Example would look something like:

@Test
public void myTest() {
    try {
        validate(new SomeObject());
    } catch (Exception e) {
        fail("expected no exception, but one was thrown.");
    }
}