Dependencies

• ActiveAnimalsManager: The singleton class being tested, which manages a set of active animals in the game.
• GameTime: A service that mimics and controls the time of the game.
• EventListener0: To ensure that the right events are triggered, a mocked event listener is used.
• ServiceLocator: Registers services used in the game to isolate the class being tested.
• GameExtension, MockitoExtension: These are JUnit extensions that allow for game-specific configuration and Mockito functionality.

Implementation

• setUp(): To guarantee test independence, the active animals set is cleaned and the singleton instance of ActiveAnimalsManager is fetched prior to each test.
• testSingletonInstance(): This test ensures that ActiveAnimalsManager follows the singleton design pattern by asserting that two calls to getInstance() return the same instance.
• testAddAnimal(): The test verifies that an animal (such as "Monkey") introduced to the manager shows up in the collection of active animals.
• testRemoveAnimal(): It confirms the ability to correctly remove an animal (like "Gorilla") introduced to the active animals set.
• testGetActiveAnimals(): The test makes sure that only the animals that have been added are returned as the correct set of active animals by the getActiveAnimals() method.