Per-parameter MethodSource analogue for CartesianTest

[jpenilla]

A way to provide values for a single parameter from a set of factory methods, similar to @MethodSource for parameterized tests would be nice to have for @CartesianTests. An example of how this might look:

    @CartesianTest
    void testDirectRoundTripStyle(
        @MethodParameterSource("dynamicOps") final DynamicOps<?> dynamicOps,
        @MethodParameterSource({"testStyles", "extraTestStyles"}) final Style style
    ) {
        testDirectRoundTrip(dynamicOps, STYLE_MAP_CODEC.codec(), style);
    }

    static List<DynamicOps<?>> dynamicOps() {
        // ...
    }

    static List<Style> testStyles() {
        // ...
    }

    static List<Style> extraTestStyles() {
        // ...
    }

I've implemented a PoC here, it's currently quite rough and copies a lot of junit internal code. If this is a concept that the maintainers are open to I can look at cleaning it up and opening a PR.

[Michael1993]

I've taken a look at your PoC. It could certainly be improved but I think you can go ahead with a PR because this is certainly something we would be interested in.

[Michael1993]

Hey, could you elaborate how this is different from @CartesianTest.MethodFactory?

[jpenilla]

The proposed @CartesianTest.MethodParameterSource is parameter-scoped and provides values for only the annotated parameter. With similar semantics to resolving values as @MethodSource does for @ParameterizedTests.

The existing @CartesianTest.MethodFactory is method-scoped, not parameter-scoped, and requires providing values for all parameters as an ArgumentSets.

The per-parameter nature makes multiple test data more easily composable without needing extraneous methods to combine the values into an ArgumentSets.

[Michael1993]

Since there is quite a bit of overlap - could you extract the common parts into our internal package (possibly as part of a new Util class)?

[Bukama]

Since there is quite a bit of overlap - could you extract the common parts into our internal package (possibly as part of a new Util class)?

Should this be an comment on the draft? :D