Do you test all the child classes of an abstract class?

gistfile1.md

So if I have a parent abstract class that is fully implemented except for the defining property number:

abstract class DividesByFive
{
	protected $number;

	public function getResult()
	{
		return $this->number / 5;
	}
}

When going to test things, I have multiple child classes based on the parent class.

I test the getResult in my SevenDividedByFive class. Do you guys test the getResult method for each of the implementations even though it is covered in our SevenDividedByFive test? Or do you just add tests for features that may differ in new children classes?

I would not even test that in the SevenDividedByFive class. Instead I would create a child class directly in the test file that inherits from DividesByFives and exists ONLY to be the single source where the methods actually implemented in DividesByFive are tested, and only because of the technicality that you can't instantiate the abstract class directly.