Idea for test suite

[evvaaaa]

In pandablocks-ioc we have a mock asyncio client which sends responses, including those of GetChanges. For example....

This ended up being pretty nasty, we're using the same responses for a bunch of unrelated tests.

With the new system we should be able to add responses directly from the test. For example

async def test_blah(mocked_panda):
    async def some_test_conditions():
         mocked_panda.add_command(...)
         mocked_panda.add_response(...)
         assert ctxt.put("PV_PREFIX:BLAH")
    ...
    # Set up `transport`
    asyncio.gather(transport.run(), some_test_conditions())

The mocked_panda will by default respond with no changes unless you add the response yourself.

[evvaaaa]

Branch with an overall system test using mock data from the real PandA:

https://github.com/PandABlocks/fastcs-PandABlocks/tree/add-system-tests

More refined and human readable response yaml can be made for specific tests.