Troubleshooting JUnit5 Testing in FXGL Games: Handling World Properties

Discover effective strategies for testing your Java FXGL game with JUnit5, including handling world properties for successful integration testing.
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This video is based on the question https://stackoverflow.com/q/65409938/ asked by the user 'testgoofy' ( https://stackoverflow.com/u/14872116/ ) and on the answer https://stackoverflow.com/a/65412741/ provided by the user 'AlmasB' ( https://stackoverflow.com/u/4861405/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting JUnit5 Testing in FXGL Games: Handling World Properties

Creating a game using Java FXGL is an exciting venture, especially for new developers exploring the world of game programming. However, as with any coding project, you may encounter hurdles along the way, such as difficulties in testing your game with JUnit5 due to uninitialized FXGL properties. This guide will walk you through the problem and provide clear solutions to ensure effective testing of your game.

The Problem at Hand

When launching tests for your Java FXGL game, the main issue arises when properties associated with the FXGL framework are not initialized. Specifically, if your game relies on accessing properties through FXGL.getWorldProperties(), your tests may not run as expected, resulting in errors or the test hanging indefinitely due to being trapped in the game loop.

Example Scenario

Suppose you have a Player class with a method to move the player. If the properties are not initialized, the tests that try to invoke this method won't work properly. Here's a simplified structure of the player code you may be testing:

[[See Video to Reveal this Text or Code Snippet]]

In situations like this, you may be tempted to call Main.main(null); in your tests to initialize the properties. However, this approach stops your tests from running due to the blocking nature of the game loop.

Suggested Solutions

There are a couple of strategies to tackle this issue and successfully run your tests.

1. Decoupling from FXGL

The most recommended approach is to modify your Player class to decouple it from FXGL. Instead of directly depending on FXGL.getWorldProperties(), ensure that your class accepts PropertyMap as a dependency. This will allow you to easily inject a mock or a simple property map during testing.

Implementation

Production Code:

[[See Video to Reveal this Text or Code Snippet]]

Test Code:

[[See Video to Reveal this Text or Code Snippet]]

This way, when you're testing, you pass in a new instance of PropertyMap, ensuring your tests can run independently of FXGL's properties being initialized.

2. Running an Integration Test

While not the most recommended method, if you want to conduct an integration test that involves the actual game environment, you can execute the entire game application in a separate thread:

[[See Video to Reveal this Text or Code Snippet]]

However, be aware that this method will block the test execution until the game ends, which is generally not ideal for unit testing as it mixes testing goals. Hence, use this approach only when necessary.

Final Thoughts

Testing your FXGL games can certainly be challenging, especially when dealing with the initialization of world properties. By decoupling your code and making Player class depend on PropertyMap, you can create a more flexible and testable structure. Alternatively, for integration tests, you can launch the entire game; however, this is not the best practice for unit tests.

With these approaches, you’re now equipped to tackle the hurdles of JUnit5 testing in your Java FXGL game. Happy coding and testing!

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