def test_definition():
length = Dimension(name="length", symbol="L", length=1)
assert length.get('length') == 1
assert length.get('time') is None
assert length.name == "length"
assert length.symbol == "L"
halflength = Dimension(name="length", length=0.5)
assert halflength.get('length') == sympify("1/2")
def test_dict_properties():
dic = {"length": sympify(1), "time": sympify(2)}
d = Dimension(dic)
assert d["length"] == 1
assert set(d.items()) == set(dic.items())
assert len(d) == 2
assert d.get("length") == 1
assert d.get("mass") is None
assert ("length" in d) is True
assert ("mass" in d) is False
