Add design note of flow testing extensions & GUI testing

[KazuhiroItoh]

This PR adds plugin extensions and GUI testing function to the flow testing design notes.

[linux-foundation-easycla[bot]]

The committers are authorized under a signed CLA.

• :white_check_mark: KazuhiroItoh (d060a1152c7b2958ec24b53f71ce345a756e01f2)

[knolleary]

Is this a proposal to add UI testing to the existing flow tester plugin that is still being developed, or to create another plugin that extends the flow tester?

I am concerned that adding UI testing to the Flow Tester plugin would make it much larger and more complicated. For most users that want to test flows, this extra size and complexity would not be needed.

I believe we still have a lot of work on the Flow Tester to do - (which I acknowledge it held up by me at the moment) so I would also be concerned about trying to add more complexity before the core is done.

If this was proposed to be a second plugin that can be installed alongside the core Flow Tester to add-in UI testing capabilities, I think that would be better.

[KazuhiroItoh]

Sorry for the late reply.

If this was proposed to be a second plugin that can be installed alongside the core Flow Tester to add-in UI testing capabilities, I think that would be better.

Yes, it is a proposal as a plugin that can add functions to the Flow Tester plugin. Users can use the UI testing feature by installing the UI testing add-on for the Flow Tester as needed.