Add a mock_all_slots option to create_thing_without_server

[julianstirling]

Adds a mock_all_slots option to create_thing_without_server. This will follow the default specified by thing_slot, so if the default is None no mock is created.

If it is a mapping with no default I think one instance is created, this needs checking in a test is tested.

• This needs unit tests before merging.

I have targeted it at #195 so the diff is clear.

Closes #198

[rwb27]

Great :) Glad this works, and it seems like it wasn't too much code to implement it.

I am thinking that it is probably a sensible idea to create a submodule called testing and move this there - along with probably a few other helpful things (like the not-yet-implemented MockServer). Hopefully that makes it easier to find and import.

[barecheck]

Barecheck - Code coverage report

Total: 94.52%

Your code coverage diff: 0.13% ▴

✅ All code changes are covered

[julianstirling]

I understand thing_slots a lot better after implementing this so that is a nice side effect. It is tested.

I think moving it to a testing module is probably a good idea. I like the idea of:

from labthings-fastapi.testing import create_thing_without_server

I think it makes it very clear that this not intended for actual use.

[rwb27]

This looks great. I've made a couple of suggestions that might be nice, but don't change the way it works meaningfully.

It would be good to move this to a testing module as we discussed, I'm happy for you to do that now, or we can do it later.

[rwb27]

What I've done in situations like this is use type narrowing:

Suggested change

	# Note that this causes mypy to throw an `attr-defined` error as _mock
	# only exists in the MockThingServerInterface
	thing._thing_server_interface._mocks.append(mock) # type: ignore[attr-defined]
	interface = thing._thing_server_interface
	if isinstance(interface, MockThingServerInterface):
	interface._mocks.append(mock)
	else:
	raise TypeError("Slots may not be mocked when a Thing is attached to a real server."

It's a bit more verbose, but it's probably a helpful check to have, as well as eliminating a type ignore.

[rwb27]

Might it make sense to do this in a separate loop? Your code above does an impressively thorough job of constructing a collection of mock Things that you can pass to attr.connect without having to mess with the ThingSlot code (which I really like). However, the first slot will not see mocked Things that are added to satisfy later slots.

Splitting the loop means all the slots see all the mocked Things, which makes it function just a little bit more like the real thing, and might catch odd edge cases where there are interactions between multiple slots. I realise that is very edge-casey, but it's a pretty minor tweak so why not...

Suggested change

	attr.connect(thing, mocks, ...)
	for attr_name, attr in class_attributes(thing):
	if isinstance(attr, ThingSlot):
	attr.connect(thing, mocks, ...)

[rwb27]

Thinking about review order, I think it might make sense to merge #194/#195 without too many more changes, then we can add the testing module and this code in a (very near) future PR.

[julianstirling]

Yeah this is only targeted to #195 so it has a sensible diff. I think aiming it at main once those are merged makes sense