Question

I am currently learning python in preperation for a class over the summer and have gotten started by implementing different types of heaps and priority based data structures.

I began to write a unit test suite for the project but ran into difficulties into creating a generic unit test that only tests the interface and is oblivious of the actual implementation.

I am wondering if it is possible to do something like this..

suite = HeapTestSuite(BinaryHeap())
suite.run()
suite = HeapTestSuite(BinomialHeap())
suite.run()

What I am currently doing just feels… wrong (multiple inheritance? ACK!)..

class TestHeap:

    def reset_heap(self):
        self.heap = None

    def test_insert(self):
        self.reset_heap()
        #test that insert doesnt throw an exception...
        for x in self.inseq:
            self.heap.insert(x)


    def test_delete(self):
        #assert we get the first value we put in
        self.reset_heap()
        self.heap.insert(5)
        self.assertEquals(5, self.heap.delete_min())

        #harder test. put in sequence in and check that it comes out right
        self.reset_heap()
        for x in self.inseq:
            self.heap.insert(x)

        for x in xrange(len(self.inseq)):
            val = self.heap.delete_min()
            self.assertEquals(val, x)

class BinaryHeapTest(TestHeap, unittest.TestCase):
    def setUp(self):
        self.inseq = range(99, -1, -1)
        self.heap = BinaryHeap()

    def reset_heap(self):
        self.heap = BinaryHeap()

class BinomialHeapTest(TestHeap, unittest.TestCase):
    def setUp(self):
        self.inseq = range(99, -1, -1)
        self.heap = BinomialHeap()

    def reset_heap(self):
        self.heap = BinomialHeap()


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

Answer 1

I personally like nose test generation more for this sort of thing. I’d then write it like:

# They happen to all be simple callable factories, if they weren't you could put
# a function in here:
make_heaps = [BinaryHeap, BinomialHeap]

def test_heaps():
    for make_heap in make_heaps:
        for checker in checkers: # we'll set checkers later
            yield checker, make_heap

def check_insert(make_heap):
    heap = make_heap()
    for x in range(99, -1, -1):
        heap.insert(x)

# def check_delete_min etc.

checkers = [
    value
    for name, value in sorted(globals().items())
    if name.startswith('check_')]