def test_expression():
p = Parser()
e = p.expression("#3")
assert isinstance(e, iec_val)
assert e.val == "3"
e = p.expression("a")
assert isinstance(e, iec_variable)
assert e.variable == "a"
e = p.expression("#2+#2")
assert isinstance(e, iec_binary_operator)
assert e.op == "+"
