def test_single():
assert_equal(x[0, 0], integrate(s, 0, 0, 0, 0))
assert_equal(x[10, 10], integrate(s, 10, 10, 10, 10))
def test_basic():
assert_equal(x[12:24, 10:20].sum(), integrate(s, 12, 10, 23, 19))
assert_equal(x[:20, :20].sum(), integrate(s, 0, 0, 19, 19))
assert_equal(x[:20, 10:20].sum(), integrate(s, 0, 10, 19, 19))
assert_equal(x[10:20, :20].sum(), integrate(s, 10, 0, 19, 19))