Question

I have an abstract class that defines some methods. This class has two subclasses.

Should I create a fake subclass just for testing, or should I test the methods through the subclasses’ tests? Testing through the subclasses seems more natural, but then I’d have to duplicate the test code between the 2 subclasses’ tests.

What do you guys think?

Answer 1

You don’t have to duplicate your test code – you can write your test methods so that they accept a parameter.

Since most test frameworks don’t support tests that take parameters you can add a little wrapper that calls your parameterized test method with a specific instance. You can now easily choose whether it makes sense to call your test just once with some specific base class, or have multiple tests of the same method – one test for each of the possible base classes. Since only a thin wrapper needs to be added for each new test, there is very little code duplication.

void TestSomething(AbstractClass foo)
{
    // Your test code goes here.
    Assert.AreEqual(42, foo.Bar());
}

[Test]
void TestSomethingFoo1()
{
    TestSomething(new Foo1());
}

[Test]
void TestSomethingFoo2()
{
    TestSomething(new Foo2());
}