import unittest

from test import test_support, seq_tests

class TupleTest(seq_tests.CommonTest):

    type2test = tuple

    def test_constructors(self):

        super(TupleTest, self).test_len()

        # calling built-in types without argument must return empty

        self.assertEqual(tuple(), ())

    def test_truth(self):

        super(TupleTest, self).test_truth()

        self.assert_(not ())

        self.assert_((42, ))

    def test_len(self):

        super(TupleTest, self).test_len()

        self.assertEqual(len(()), 0)

        self.assertEqual(len((0,)), 1)

        self.assertEqual(len((0, 1, 2)), 3)

    def test_iadd(self):

        super(TupleTest, self).test_iadd()

        u = (0, 1)

        u2 = u

        u += (2, 3)

        self.assert_(u is not u2)

    def test_imul(self):

        super(TupleTest, self).test_imul()

        u = (0, 1)

        u2 = u

        u *= 3

        self.assert_(u is not u2)

    def test_tupleresizebug(self):

        # Check that a specific bug in _PyTuple_Resize() is squashed.

        def f():

            for i in range(1000):

                yield i

        self.assertEqual(list(tuple(f())), range(1000))

    def test_hash(self):

        # See SF bug 942952:  Weakness in tuple hash

        # The hash should:

        #      be non-commutative

        #      should spread-out closely spaced values

        #      should not exhibit cancellation in tuples like (x,(x,y))

        #      should be distinct from element hashes:  hash(x)!=hash((x,))

        # This test exercises those cases.

        # For a pure random hash and N=50, the expected number of occupied

        #      buckets when tossing 252,600 balls into 2**32 buckets

        #      is 252,592.6, or about 7.4 expected collisions.  The

        #      standard deviation is 2.73.  On a box with 64-bit hash

        #      codes, no collisions are expected.  Here we accept no

        #      more than 15 collisions.  Any worse and the hash function

        #      is sorely suspect.

        N=50

        base = range(N)

        xp = [(i, j) for i in base for j in base]

        inps = base + [(i, j) for i in base for j in xp] + \

                     [(i, j) for i in xp for j in base] + xp + zip(base)

        collisions = len(inps) - len(set(map(hash, inps)))

        self.assert_(collisions <= 15)

    def test_repr(self):

        l0 = tuple()

        l2 = (0, 1, 2)

        a0 = self.type2test(l0)

        a2 = self.type2test(l2)

        self.assertEqual(str(a0), repr(l0))

        self.assertEqual(str(a2), repr(l2))

        self.assertEqual(repr(a0), "()")

        self.assertEqual(repr(a2), "(0, 1, 2)")

def test_main():

    test_support.run_unittest(TupleTest)

if __name__=="__main__":

    test_main()