Introducing ResourceBundle for Player Resources and Expanding Unit Test Coverage

TLDR

Introducing ResourceBundle class to represent the set of resources that a player has. Updating business logic and JSON serialization to leverage new ResourceBundle. Refactoring RollResult logic to be more testable. Adding unit test coverage to existing code / logic.

Mocking static method calls.

public class CatanGameTest {

  // mock calls to the random number generator
  MockedStatic<RollResult> mockedRollResult;

  // TODO not needed for most tests
  @BeforeEach
  public void beforeEach() {
    mockedRollResult = Mockito.mockStatic(RollResult.class);
    mockedRollResult.when(RollResult::getRandomNumber)
        .thenReturn(3)
        .thenReturn(3)
        .thenReturn(2)
        .thenReturn(2)
        .thenReturn(1)
        .thenReturn(1);
  }

  @AfterEach
  public void afterEach() {
    mockedRollResult.close();
  }

  .
  .
  .
}

Main work

• Define the ResourceBundle class and its add() and increment() instance methods.
• Updating the Player model’s resource field to use the new ResourceBundle type.
  • This required use of Jackson @JsonUnwrapped annotation.
• Finding a way to mock the random roll logic for unit testing.
  • Ultimately landed on the MockedStatic<T> class from Mockito.

Challenges

• Having to mock static methods always feels awkwards and begs the question: “Is this designed poorly?”.
  • Not all unit tests within the suite actually need the @BeforeEach logic to run, either.
• Now at the point where making changes will be safer because of test coverage, but will require test updates / compilation fixes.

Learnings

• Adding a lombok.config file with lombok.addLombokGeneratedAnnotation = true will mark all Lombok code with @Generated annoation.
  • This allows Jacoco to ignore getter / setter / etc. code from Lombok when it computes code coverage percentages.
• @JsonUnwrapped was very nice for resolving the nested JSON created by my new data structure.
  • e.g., player.resources looked like this before the annoation:

    {
      "resources": {
        "resourceBundle": {
          "0": 0,
          "1": 0,
          "2": 0,
          "3": 0,
          "4": 0
        }
      }
    }

• Must have been tired, because I was confused about how my ResourceBundle class could access the private instance variables of other ResourceBundle instances. That is just default behavior of private, no need for protected.
  • e.g., look at the add(ResourceBundle other) method.
  • other’s private instance variables are still accessible.