def test_delegate_parameter_get_and_snapshot_with_none_source():
"""
Test that a delegate parameter returns None on get and snapshot if
the source has a value of None and an offset or scale is used.
And returns a value if the source is remapped to a real parameter.
"""
none_param = Parameter("None")
source_param = Parameter('source',
get_cmd=None,
set_cmd=None,
initial_value=2)
delegate_param = DelegateParameter(name='delegate', source=none_param)
delegate_param.offset = 4
assert delegate_param.get() is None
assert delegate_param.snapshot()['value'] is None
delegate_param.offset = None
delegate_param.scale = 2
assert delegate_param.get() is None
assert delegate_param.snapshot()['value'] is None
assert delegate_param.cache._parameter.source.cache is none_param.cache
delegate_param.source = source_param
assert delegate_param.get() == 1
assert delegate_param.snapshot()['value'] == 1
assert delegate_param.cache._parameter.source.cache is source_param.cache
def test_delegate_parameter_get_and_snapshot_raises_with_none():
"""
Test that a delegate parameter raises on get and snapshot if
the source has a value of None and a scale is used.
But works correctly if the source is remapped to a real parameter.
"""
none_param = Parameter("None")
source_param = Parameter('source', get_cmd=None, set_cmd=None, initial_value=2)
delegate_param = DelegateParameter(name='delegate', source=none_param)
delegate_param.scale = 2
with pytest.raises(TypeError):
delegate_param.get()
with pytest.raises(TypeError):
delegate_param.snapshot()
assert delegate_param.cache._parameter.source.cache is none_param.cache
delegate_param.source = source_param
assert delegate_param.get() == 1
assert delegate_param.snapshot()['value'] == 1
assert delegate_param.cache._parameter.source.cache is source_param.cache
