Which technique should be used for testing abstract class functionality in PHPUnit?

Question

I know three approaches:

1. Create fake subclass (looks ugly)
2. Test one of real subclasses
3. Use getMockForAbstractClass() (contradicts with mocks' mission; also can't stub not-abstract methods)

What the best way according unit test concept?

Answer 1

I would only write tests for concrete classes derived from the abstract class. If you find you are duplicating tests among them, write a superclass and move the duplicated tests there or use getMockForAbstract class for these.

So if you had something like this:

abstract class Employee
{
    protected $name;
    public function getName()
    {
        return $this->name;
    }
    abstract function doWork();
    …
}

class Mechanic extends Employee
{
    public function doWork()
    {
        return // specific to Mechanic
    }
}

class Engineer extends Employee
{
    public function doWork()
    {
        return // specific to Engineer
    }
}

I'd have a test class for Mechanic and Engineer testing their doWork implementation, but not their getName functionality, because that is inherited by the abstract class. For that, I'd write a custom class then or use getMockForAbstractClass, as shown in the example in the PHPUnit Manual:

• http://www.phpunit.de/manual/3.6/en/test-doubles.html#test-doubles.mock-objects

Answer 2

It depends on how functional the abstract class is. When the abstract class is merely there to provide some basic boilerplate with a bunch of template methods, I limit my testing to the concrete subclasses.

When the abstract class is mostly complete I will either create a concrete subclass for the test in the same file as the test case or I will use a mock. Note that getMockForAbstractClass() is just a helper that finds all the abstract methods for you. There's nothing stopping you from declaring all the abstract methods plus some concrete ones with getMock(). For this very reason I override getMock() in our base test case to merge in all the abstract methods before calling the parent.