from inspect import isclass
import unittest
from peak.rules import when, abstract

class A(object): pass
class B(A): pass

@abstract
def whats_this(obj):
    pass

@when(whats_this, "isclass(obj) and issubclass(obj, A)")
def say_it(obj):
    return "It's an A!"

@when(whats_this, "isclass(obj) and issubclass(obj, B)")
def say_it(obj):
    return "It's a B!"

@when(whats_this, (B,))
def say_it(obj):
    return "It's an B instance!"

@when(whats_this, (A,))
def say_it(obj):
    return "It's an A instance!"

class TestTypeImplications(unittest.TestCase):
    def test_issubclass_B_implies_issubclass_A(self):
        self.failUnlessEqual(whats_this(B), "It's a B!")
        self.failUnlessEqual(whats_this(A), "It's an A!")
        
    def test_isinstance_B_implies_isinstance_A(self):
        self.failUnlessEqual(whats_this(B()), "It's a B instance!")
        self.failUnlessEqual(whats_this(A()), "It's an A instance!")

if __name__ == "__main__":
    unittest.main()