def test_one(self):
'''Allow 'composing' just 1 function'''
assert compose(self.double)(2) == 4
def test_order(self):
'''Compose in the right order'''
assert compose(self.double, self.add)(2) == 2 * (2+1)
assert compose(self.add, self.double)(2) == 1 + 2*2
def test_empty(self):
'''When composing nothing, ValueError'''
with pytest.raises(ValueError):
compose()
