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javajunitmockitopowermockassertj

AnyString() as parameter for unit test

I have to deal with a legacy application that has no tests. So before I begin refactoring I want to make sure everything works as it is.

Now imagine the following situation:

public SomeObject doSomething(final OtherObject x, final String something) {
    if(x == null) throw new RuntimeException("x may not be null!");
    ...
}

Now I want to test that null check, so to be sure it works and I don't lose it once I refactor.

So I did this

@Test(expected = RuntimeException.class)
public void ifOtherObjectIsNullExpectRuntimeException() {
    myTestObject.doSomething(null, "testString");
}

Now, this works of course.

But instead of "testString" I'd like to pass in a random String.

So I tried with:

@Test(expected = RuntimeException.class)
public void ifOtherObjectIsNullExpectRuntimeException() {
    myTestObject.doSomething(null, Mockito.anyString());
}

But this is not allowed., as I get

org.mockito.exceptions.misusing.InvalidUseOfMatchersException: ... You cannot use argument matchers outside of verifications or stubbing

I do understand the meaning of this, but I wonder whether I can still manage to do what I want without parameterizing my test or the like. The only libraries I may use are Junit, AssertJ, Mockito and Powermock.

Any ideas?

Solution

  • Well, like Mockito is trying to tell you via that exception, that's not really how you'd use anyString. Such methods are only to be used by mocks.

    So, why not try testing with an actual random string? My personal favorite in such a scenario: java.util.UUID.randomUUID().toString(). This will virtually always generate a brand new string that has never been used for your test before.

    I'd also like to add that if you are writing tests for your SomeObject class that you should avoid mocking SomeObject's behavior. From your example, you weren't exactly doing that, but it looked like you might be going down that route. Mock the dependencies of the implementation you're trying to test, not the implementation itself! This is very important; otherwise you aren't actually testing anything.