JUnit @ParametrizedTest Class Objects as Value Source?

Question

I would like to create a ParametrizedTest that tests a bunch of different AIs at the same time, making sure that the don't take too long to do their calculations. However, I cannot create new Objects in the ValueSource, so I'm unsure how to proceed.

The problem is that I need to pass constant values to ValueSource, which is where I get stuck. How can I make my objects constant?

 @ParameterizedTest
  @ValueSource(ais = {new AdvancedAI(), new blabla})
  public void moveCalculatedInTimeBy(AI TestAI) {
    long startTime = System.currentTimeMillis();
    Turn turn = Turn.initialTurn();
    Move calculatedMove = TestAI.calculateMove(Optional.empty(), turn);
    long endTime = System.currentTimeMillis() - startTime;
    assertTrue(endTime <= 8000);
  }

Answer 1

Using @ValueSource is for simple arguments, the kind that can be set as values to annotation elements. In other words, primitives, strings, and classes ¹ . Since you want to provide instances of a class this won't work for you. Instead, you'll want to use something like @MethodSource ² .

@ParameterizedTest
@MethodSource("testAiProvider")
void moveCalculatedInTimeBy(AI testAI) {
  // perform test...
}

static List<AI> testAiProvider() {
  // return List of test AI instances
}

See the user guide and Javadoc for more information, such as what return types are allowed for factory methods.

---

^{1. Enum constants can also be used in annotations, but you can't make a generic enum annotation element. That's why JUnit 5 also has @EnumSource .}

^{2. You can also use @ArgumentsSource directly, which lets you define an ArgumentsProvider , if you need it.}