def test_edge_cases():
assert merge() == None
assert merge(42) == 42
def test_merge_difftype():
with pytest.raises(TypeError):
merge(42, 'hello')
def test_hole():
assert merge('hello {_}', 'world') == 'hello world'
assert merge('world', 'hello {#}') == 'hello world'
with pytest.raises(TypeError):
merge('{_}', '{#}')
def test_merge_unknown():
assert merge(object(), 42) == 42
assert merge(None, 42) == 42
assert merge(lambda: 42, 42) == 42
def test_merge_bool():
assert merge(True, False) == False
def test_merge_string():
assert merge('hello', 'world') == 'world'
def test_merge_dict3():
a = dict(b=dict(c=[42]))
b = dict(b=dict())
assert merge(a, b) == dict(b={'c': [42]})
def test_merge_dict2():
a = dict(a=42, b=[42])
b = dict(b=[])
assert merge(a, b) == dict(a=42, b=[42])