How can you use unit testing to catch bugs in game development?

From my experience, the most crucial benefits were: 1. Better quality of code - for many reasons you will not be able to write pure unit tests in high-tightened like spaghetti code. 2. To run 1000 unit tests is cheaper than 1 UI test - that saves hardware resources for CI/CD 3. Developers better understand the code - the main benefit. Good Unit tests will help understand faster the code for new developers. 4. You get the most benefits if unit tests are written with a strict code style. Usually, high unit test coverage will not correlate significantly with end production quality for players for client development. That is why you should include other types of tests in your Quality pipeline like e2e, integration, functional tests, etc.

Here is my personal top 3 benefits of having unit tests in the project: 1. 'Free' regression testing: good unit tests can protect against bugs in the future during adding/changing/refactoring code for new features or bugfixes. Tests take the role of QA that does everything very quickly and can do it in any time. It is important to understand that test cannot fully replace QA. 2. Incresing project code quality: it is hard to write unit tests for bad code. So unit tests force to produce better code (follow SOLID principles). 3. Serves as documentation: Unit tests can show and demonstrate expecting behavior. Compared with documentation, they can not outdate because they fail immediately. They are more reliable than documentation.

In the dynamic world of game development, unit testing emerges as a crucial ally. By breaking down code into testable units, developers can catch bugs early, ensuring a seamless gaming experience. This proactive approach not only enhances code quality but also saves time and resources by preventing issues from escalating. Unit testing fosters collaboration among teams and promotes a culture of continuous improvement. Embrace the power of unit testing to create bug-free, captivating games!

For us the value of unit-testing in game-development is to reduce the surface area for the QA departement. A big part of game-development is writing decoupled systems that integrate in your game as a whole. By covering these systems with unit-tests the logic can be tested fairly easily. The hard part of QA in games is about verifying that systems work well together. You can only get this far with integration tests, so a big part of testing falls in the hands of the QA department or even alpha and beta releases to the end-users. A comprehensive suite of tests can significantly reduce the work the QA department has to do. This way they can focus on 'exploratory testing' instead of testing the login sequence over and over again.

Verifying the performance of a game through unit tests might be limited. Performance testing often requires profiling tools and analysis during runtime, which is not typically covered by unit tests

Challenges of unit-testing in game-development come from non-orthogonal systems. When systems are to tightly coupled it's very hard to test since unit-tests need to run in isolation. A good OO design combats such tight coupling. When systems can be mocked and controlled from the outside during testing you can setup the right environment per test scenario. A common 'problem' in testing games is temporal coupling. This means that time itself is a variable in tests cases, and this time needs to be controlled. So for Unity3D that might mean you need to explicitly move time forward with a custom Update loop. This means your code must be decoupled from the update loop to be tested properly. Sometimes, this will be tricky to pull off.

In Game Client Development writing Unit Tests can be hard for many reasons. It depends on the type and architecture of the game, team resources, game engine etc. For Unity, you can take Unity Test Framework. UTF provides 2 types of tests: Playmode and Editmode. Editmode tests are most similar to pure Unit tests. List of main best practices from my point of view: 0. First read Unit testing best practices with .NET Core and .NET Standard from Microsoft. That is basic. 1. Use the Arrange-Act-Assert pattern with the proper naming of the test. And prefer Assert. That 2. Do not overuse mocks. 3. Automate running your tests in CI/CD 4. Cover your production code 5. Don't aim for 100% tests coverage Keep in mind Unit tests don't guarantee 0 bugs.

Considering the points I described earlier; a good strategy for unit-testing games is to create loosely coupled systems. Such systems need to be easily swapper for mocks or test stubs. During testing you can focus on the busines logic and narrow the surface the QA testers need to cover. Make sure you control all the inputs like the database, ui and even time. Oo code is often designed based on abstract / interfaces and during testing these interfaces can be implemented using mocks. QA can therefore focus on testing features impacted by UI, physics, real-time connections and do some exploratory testing. This way both development and QA can deliver the most value.

In Unity game development, effective unit testing practices are crucial for maintaining code quality and identifying bugs early in the development process. Best practices include incorporating unit tests early in the development cycle, automating the testing process using Unity's testing framework, and ensuring comprehensive coverage of critical code paths and functionalities. Utilizing Unity's built-in testing tools, developers can run tests automatically, facilitating quick feedback and prompt bug resolution. By adhering to these practices, Unity developers can enhance the reliability and stability of their games throughout the development lifecycle.

Probably the most important aspect of getting great unit-tests on a project is to have all members of the team contributing. When it's only you or just a tiny part of the team that sees the value in testing you will be fighting an uphill battle. So make sure you convince your team members. Also, try to find an architecture that fits the problem you are solving. Don't try to fit the new shiny architecture to your problem, it must be the other way around; design an archtecture around your problem. Try to keep things simple because simplicity is a prerequisite for robustness. Try and find the testing frameworks for your engine and use learn to use them. They will probably simplify things further. Last; investigate TDD ;)