PHPUnit, Testing "Behaves Like A..."

I have a series of PHPUnit tests to validate a class, "Class A".

I have another class, "Class B" which extends Class A.

Is there a good way to test that "Class B passes Class A's tests", or开发者_JS百科 in other words "Class B behaves like Class A" without duplicating the test code?

I could test for the extends (using instanceof), but that seems like a misleading test.

I care that it behaves like Class A, not that it extends Class A, right? or wrong?

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Just extend the PHPUnit test case of class A, for class B, that should do it.