As it stands the creation of dynamic tests via test factory methods is, from a coding experience perspective, no improvement over simple looping:

    // should be executed for different points and distances
    void testDistanceComputation(Point p1, Point p2, double distance) {
        assertEquals(distance, p1.distanceTo(p2));
    }

    @Test
    void testDistanceComputations() {
        createTestData().forEach(testData -> 
            testDistanceComputation(datum.point1(), datum.point2(), datum.distance()));
        }
    }

    @TestFactory
    Stream<DynamicTest> testDistanceComputations() {
        return DynamicTest.stream(
            createTestData(),
            datum -> "Testing " + datum,
            datum -> testDistanceComputation(datum.point1(), datum.point2(), datum.distance()));
    }

I see a couple of ways in which extensions could improve this situation but for that an extension point for dynamic test generation is needed.

My intuition is to create an extension interface, whose implementations must be registered on the test class and would be called at exactly the same point where @TestFactory is resolved now. They would have to return a stream of dynamic tests, which were then processed like those of test factories. Ideally @TestFactory would use the same mechanism.

This should give extensions plenty of room to create tests, especially parameterized ones, much more conveniently.

Related Issues

• Allow hierarchical parameterized/dynamic tests #604
• Introduce Extension API for registering dynamic tests #1444