Provide a way to generate deeper test trees using `@ParameterizedTest`

[britter]

@ParameterizedTest is a great feature to implement data-driven tests with little boilerplate code. The introduction of Named and the changes in #3818 further improved this by making it easier to assign names to argument sets.

However if I want to further group my arguments, I need to use more complex features such as @Nested or @TestFactory. It would be great if @ParameterizedTest provided a way to introduce deeper nesting in the test tree.

For example with the following:

@MethodSource("provideGrouped")
@ParameterizedTest
void test(String name, int value) {
// ...
}

static Stream<Arguments> provideGrouped() {
  return Stream.of(
    argumentSet("group-1", arguments("one", 1), arguments("two", 2)),
    argumentSet("group-2", arguments("Monday", 1), arguments("Tuesday", 2)),
  );
}

I'd like to have the following test tree:

- test(String, int)
-- group-1 
---- "one", 1
---- "two", 2
-- group-2
---- "Monday", 1
---- "Tuesday", 2

Of course this should work with deeper nesting, @ParameterizedClass, and nested Named arguments ;)

Deliverables

• Deeply nested test trees based on @ParameterizedTest and Arguments

[kaipe]

LazyParams is not really designed for these scenarios but nevertheless it is possible to introduce one additional nesting level for those argument-set names by using this little function ...

import java.util.stream.Stream;
import org.junit.jupiter.params.provider.Arguments.ArgumentSet;

import static org.lazyparams.LazyParamsCoreUtil.makePick;
import static org.lazyparams.LazyParamsCoreUtil.displayOnSuccess;

public class StreamPicker {

    public static Stream pickArgsetStreamByName(ArgumentSet... argSets) {
        Object paramId = new Object() {}.getClass();
        ArgumentSet picked = argSets[makePick(paramId, true, argSets.length)];
        displayOnSuccess(paramId, " " + picked.getName());
        return Stream.of(picked.get());
    }
}

... instead of Stream.of(...):

@MethodSource("provideGrouped")
@ParameterizedTest
void test(String name, int value) {
// ...
}

static Stream<Arguments> provideGrouped() {
    return StreamPicker.pickArgsetStreamByName(
        argumentSet("group-1", arguments("one", 1), arguments("two", 2)),
        argumentSet("group-2", arguments("Monday", 1), arguments("Tuesday", 2))
    );
}

// Test-result when all tests pass:
//
// ─ TheTestClass ✔
//  └─ test(String, int) ✔
//     ├─ test(String, int) group-1 ✔
//     │  ├─ [1] "one", 1 / ✔
//     │  └─ [2] "two", 2 / ✔
//     └─ test(String, int) group-2 ✔
//        ├─ [1] "Monday", 1 / ✔
//        └─ [2] "Tuesday", 2 / ✔

[mpkorstanje]

Notes for team discussion:

• Arguments are consumed by parameterized tests and parameterized classes
• Looks like the the dynamic descendant filter only works on top level for both templates and test factories.

[marcphilipp]

Team decision: Wait for additional interest from the community.