- Increased revenue potential
- Enhanced debugging
- Improved scalability
However, to achieve these benefits, unit tests should be easily readable and resilient; poorly written or designed tests can be challenging to execute and maintain. This article provides an overview of unit testing and highlights 10 unit testing best practices for businesses.
What is unit testing?
Unit testing ensures that each component of the software is operating as intended. A function, procedure, method, object, or module can all be considered units. Unit tests are usually automated and contribute to early-stage (coding stage) code quality assurance.
Below you can see the place of unit testing among other software testing practices, such as integration testing, system testing, and acceptance testing.
Figure 1: Levels of Software Testing
10 Unit Testing Best Practices
1. Name Your Tests
If you aim to build a test-driven development, you should name your tests. Tests provide documentation in addition to verifying the functionality of your code. When you name a test, you indicate the test’s goal explicitly.
You should be able to determine the behavior of your code just by looking at the collection of unit tests without ever opening the code itself. Additionally, you can see precisely which situations fall short of your expectations when tests fail.
The two figures below (Figure 2 & Figure 3) compare a bad and a good example of naming unit tests. A good unit test name should explicitly state what the test case is intended to do.
Figure 2: A bad example of naming unit tests
Figure 3: A better example of naming unit tests
2. Write readable unit tests
One of the most crucial considerations when developing a test is readability. When writing unit tests, the test runner can use the ‘AAA’ pattern for unit testing;
- Arrange: Plan the test’s initialization and setup
- Act: Call an action on the unit for the given test
- Assert: Verify the operation’s outcome to ensure it functioned as expected.
Separating these three actions will highlight the dependencies required to call your code, how your code is being called, and what you’re trying to assert.
3. Automated unit testing
Using a unit testing framework, choose automated unit testing. Automating tests in your continuous integration (CI/CD) pipeline will be a better strategy. Test automation and automated unit tests can reduce test defects and failures by 20%.2
Manually testing small units is very time-consuming and has proven less trustworthy. 3
Testifi offers CAST, a test automation tool. Using a test-first strategy, the firm supports businesses on the road to providing high-quality software and accelerating release cycles. It is a low-code test automation tool, making quality assurance less complicated.
4. Write unit tests during the development process
Unit tests are the first carried out during the development cycle and are located at the bottom of the testing pyramid (Figure 1). They, therefore, function best when carried out concurrently with development.
Early unit testing encourages producing clean code and helps find errors as soon as possible. If you aim to follow the test-driven development approach, making unit tests part of the build process will be crucial, especially for automated tests.
5. Pay attention to interdependencies
Interdependencies between tests make them unstable, challenging to execute, and difficult to debug. Test runners typically run numerous unit tests simultaneously without adhering to any specific order. To prevent test interdependence, ensure each test case has its setup and teardown procedures.
Consider the scenario where a new test is added without its own setup while the test runner is already running a few tests in a specific order. Now, if the test runner runs every test concurrently to cut down on execution time, the entire test suite would become disoriented, and your tests would start failing.
6. Avoid using manual concentration
Avoid logical conditions like ‘if,’ ‘while,’ ‘for,’ and ‘switch’ as well as other circumstances while designing your unit tests. When you avoid using logical conditions, there will be less chance of introducing a bug inside your tests. You will be more focused on the end result than the implementation process.
7. Avoid testing multiple scenarios per test
Each unit test should concentrate on a single assertation and confirm that the results match what is anticipated for the tested method. If you concentrate on just one use case rather than evaluating multiple use cases, you’ll have a better understanding of the underlying issue if the test fails.
For example, sometimes, one set or scenario may contain multiple asserts. In such situations, even if there has been a single failure, all assertions will require you to review them to determine the problem’s primary cause.
8. Write deterministic tests
You should write tests that have consistent behavior. For instance, If a test is executed 10 times, it should succeed or fail 10 times. If a test succeeds only half of the time, it does not contribute to the software development; there is no in-between when it comes to deterministic tests.
To create deterministic unit tests, make sure they are independent of one another and do not rely on:
- Environmental values (e.g., language settings, computer operating system)
- External dependencies (e.g., file system, network, APIs)
- Other test cases
Creating deterministic, independent unit tests will be beneficial because they will be able to work in any setting. For example, a test written in a specific language setting will not work in another. Developing teams won’t trust your tests if they are not deterministic.
9. Write simple tests
To validate the behavior you’re currently testing, the input used in a unit test should be as simple as it can be. Writing simple tests will reduce the likelihood of future breakages when the codebase requires changes. More information than necessary to pass a test increases the risk of test errors and obscures the test’s intended purpose.
10. Update your tests
Continuously review and update your tests as the code and requirements change. Unit tests are suitable for long-term projects because they provide new team members with thorough documentation by simplifying the code and its behavior. This will also help your quality assurance team to avoid test failures.
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