applet: extract test code to a separate file.

[wanda-phi]

Fixes #447.

[whitequark]

H-how did you do it so quickly?!

[whitequark]

But yeah the test.py wrapper can now be removed, a PDM test script that runs some normal unittest invocation can be added, and for glasgow test we need some sort of loader that I'm not yet sure how to hack together but I'm sure something can be done about it.

[whitequark]

So right now GlasgowApplet maintains a registry of applet test cases (IIRC) which wouldn't work anymore unless each test module is imported when the applet itself is imported (which we probably don't want), but I'm not sure exactly how to replace that.

[wanda-phi]

Mhm. I suppose you'd also want the testcases outside of applets extracted to test_*.py files before getting rid of the custom test.py entrypoint, right?

[whitequark]

I suppose you'd also want the testcases outside of applets extracted to test_*.py files before getting rid of the custom test.py entrypoint, right?

Inevitably, yeah.

[whitequark]

For non-applets the tests should be in a top-level directory tests/, that exists side-by-side with software/glasgow/. (For applets we break this rule to make applets contained within a single directory, which is something I want to keep forever.)

[wanda-phi]

For non-applets the tests should be in a top-level directory tests/, that exists side-by-side with software/glasgow/. (For applets we break this rule to make applets contained within a single directory, which is something I want to keep forever.)

It seems we cannot have the directory at top level (AssertionError: Path must be within the project), I'm going to do software/tests.

[whitequark]

I'm going to do software/tests.

Yes sorry, I meant under software/tests/ and was unclear.

[wanda-phi]

OK, this should now be done except for the glasgow test fixups.

[whitequark]

except for the glasgow test fixups.

How about this as an approach for glasgow test:

1. We remove the registration done in GlasgowAppletTestCase; applet.test_cls is now not a thing.

2. For each applet, we have code that looks something like this:

   @classmethod
   def tests(cls):
       from . import test # this way the name of the test case is only repeated once :3
       return (test.FooAppletTestCase,)
   

   The return value of tests (a new abstract method defined on GlasgowApplet) is something that can be directly passed to unittest.TestSuite() constructor.

3. In the CLI we use the normal discovery mechanisms, without the mutating-state-on-import that GlasgowAppletTestCase is currently using.

Sounds good?

[whitequark]

Fantastic work as usual, @mwkmwkmwk!

[whitequark]

@attie Looks like I cannot merge this without your consent as a code owner (!), which would be appreciated ASAP.

[attie]

Not reviewed in detail, but looks like a good step to me - thanks both!