Add a shared parent mock for all signals in once device

[DominicOram]

As a developer I occasionally want to make sure that one signal is changed before another. For example, see test_retrieve_mock_and_assert in https://github.com/bluesky/ophyd-async/pull/335/files or for a more real world example see numerous tests in https://github.com/DiamondLightSource/dodal/blob/main/tests/devices/unit_tests/test_aperture_scatterguard.py. To do this you need to create a parent mock that all the signals are children of.

If ophyd_async by default made all the mock's in one device have the same parent this would remove a bit of boilerplate from downstream.

[coretl]

A suggestion for implementation:

• Change Device.connect to take mock: Union[bool, Mock] = False
• If isinstance(mock, Mock) then use it as the mock for the Device, otherwise create a new one
• When calling child.connect, then call mock.attach_mock(child_name, child_mock) and pass mock=child_mock to the child

This will mean that if you have a tree of devices where connect it called at the top level then you can call:

get_mock_put(mydevice).assert_has_calls(
        [
            call.child1.grandchild1(100, wait=True, timeout=ANY),
            call.child2.grandchild2(67, wait=True, timeout=ANY),
        ]
    )

I'm a little concerned that we might decide we want to check the ordering of puts and other methods like get_descriptor, so maybe we should consider this before making a mock heirarchy we rely upon?

For instance, would we ever want something like this?

get_mock(mydevice).assert_has_calls(
        [
            call.child1.grandchild1.put(100, wait=True, timeout=ANY),
            call.child1.grandchild1.get_descriptor(),
            call.child2.grandchild2.put(67, wait=True, timeout=ANY),
        ]
    )

@DominicOram thoughts?

[coretl]

@DominicOram any thoughts on this?

[coretl]

@dperl-dls any thoughts on this?

[DominicOram]

A suggestion for implementation:

Yes, I like this idea.

I'm a little concerned that we might...

This feels like feature creep at this point. I can't see a reason we would want to do this yet and it doesn't seem like the way we structure this hierarchy will have that much of an affect on how we want to do it in the future.

[coretl]

This feels like feature creep at this point. I can't see a reason we would want to do this yet and it doesn't seem like the way we structure this hierarchy will have that much of an affect on how we want to do it in the future.

Ok, let's go with the minimum change then, so

get_mock_put(motor.setpoint).assert_called_once_with(32.0, wait=True, timeout=ANY)

will still work, and so will:

get_mock_put(motor).assert_has_calls(
        [
            call.setpoint(32.0, wait=True, timeout=ANY),
            call.velocity(1.0, wait=True, timeout=ANY),
        ]
    )