test_core.py 文件源码

def test_EmptyMapping():
    marker = object()

    # It should be possible to 'construct' an instance..
    assert EmptyMapping() is EmptyMapping

    # Must be passable to dict()
    assert dict(EmptyMapping) == {}

    # EmptyMapping['x'] raises in various forms.
    assert 'x' not in EmptyMapping
    with pytest.raises(KeyError):
        EmptyMapping['x']
    with pytest.raises(KeyError):
        del EmptyMapping['x']

    EmptyMapping['x'] = 4  # Shouldn't fail

    assert 'x' not in EmptyMapping  # but it's a no-op
    with pytest.raises(KeyError):
        EmptyMapping['x']

    # Check it's all empty
    check_empty_iterable(EmptyMapping, 'EmptyMapping')
    check_empty_iterable(EmptyMapping.keys(), 'keys()')
    check_empty_iterable(EmptyMapping.values(), 'values()')
    check_empty_iterable(EmptyMapping.items(), 'items()', item=('x', 'y'))

    # Dict methods 
    assert EmptyMapping.get('x') is None
    assert EmptyMapping.setdefault('x') is None

    assert EmptyMapping.get('x', marker) is marker
    assert EmptyMapping.setdefault('x', marker) is marker
    assert EmptyMapping.pop('x', marker) is marker

    with pytest.raises(KeyError):
        EmptyMapping.popitem()
    with pytest.raises(KeyError):
        EmptyMapping.pop('x')

    assert not EmptyMapping

    assert len(EmptyMapping) == 0

    # Should work, but do nothing and return None.
    assert EmptyMapping.update({1: 23, 'test': 34, }) is None
    assert EmptyMapping.update(other=5, a=1, b=3) is None

    # Can't give more than one mapping as a positional argument,
    # though.
    with pytest.raises(TypeError):
        EmptyMapping.update({3: 4}, {1: 2})

    # Check it's registered in ABCs.
    from collections import abc
    assert isinstance(EmptyMapping, abc.Container)
    assert isinstance(EmptyMapping, abc.Sized)
    assert isinstance(EmptyMapping, abc.Mapping)
    assert isinstance(EmptyMapping, abc.MutableMapping)