def test_egcd_consistency(a, b):
d, x, y = extended_gcd(a, b)
if a == b == 0:
assert d == x == y == 0
elif a == 0:
assert d == b and x == 0 and y == 1
elif b == 0:
assert d == a and x == 1 and y == 0
else:
qa = max(1, (a / d) / 2)
qb = max(1, (b / d) / 2)
assert (a % d == 0 and b % d == 0
and a * x + b * y == d
and -qb <= x <= qb
and -qa <= y <= qa)
def test_egcd_reversed(a, b):
if a != b:
d0, x0, y0 = extended_gcd(a, b)
d1, x1, y1 = extended_gcd(b ,a)
assert (d0, x0, y0) == (d1, y1, x1)
def test_egcd_ret_type(a ,b):
d, x, y = extended_gcd(a, b)
assert_is_integer(d)
assert_is_integer(x)
assert_is_integer(y)
def test_egcd_known(a, b, d, x ,y):
assert (d, x, y) == extended_gcd(a, b)
def test_egcd_seq_type(a, b):
assert type(extended_gcd(a, b)) == tuple