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_with_changed_source_snapshot_matches_value(
value, scale, offset):
delegate_param = DelegateParameter(name="delegate",
source=None,
scale=scale,
offset=offset)
source_parameter = Parameter(name="source",
get_cmd=None,
set_cmd=None,
initial_value=value)
_assert_none_source_is_correct(delegate_param)
delegate_param.source = source_parameter
calc_value = (value - offset) / scale
assert delegate_param.cache.get(get_if_invalid=False) == calc_value
assert delegate_param.source.cache.get(get_if_invalid=False) == value
snapshot = delegate_param.snapshot()
# disregard timestamp that might be slightly different
snapshot["source_parameter"].pop("ts")
source_snapshot = source_parameter.snapshot()
source_snapshot.pop("ts")
assert snapshot["source_parameter"] == source_snapshot
assert snapshot["value"] == calc_value
assert delegate_param.get() == calc_value
# now remove the source again
delegate_param.source = None
_assert_none_source_is_correct(delegate_param)
_assert_delegate_cache_none_source(delegate_param)
def test_set_source_cache_changes_delegate_get(simple_param):
""" When the delegate parameter's ``get`` is called, the new
value of the source propagates.
"""
offset = 4
scale = 5
d = DelegateParameter('d', simple_param, offset=offset, scale=scale)
new_source_value = 3
simple_param.cache.set(new_source_value)
assert d.get() == (new_source_value - offset) / scale