JavaBest Practices for Unit Testing in Java

Best Practices for Unit Testing in Java

Unit testing helps us catch bugs and regressions before they make it into production environments, which saves time and money. However, there are certain best practices that need to be followed in order to make sure that you get the maximum benefits from unit testing your Java application’s code.

This programming tutorial talks about unit testing, why it is important, and the best practices of unit testing your application’s source code written in Java.

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What is Unit Testing in Java?

Unit Testing is a technique for testing individual units of source code to ensure that they work as desired. In other words, unit testing is used to ensure the smallest possible testable parts of an application are tested to make sure that they work correctly.

Unit tests are usually written by developers, who use unit tests to make sure their code works as expected and does not break any other part of the program. Unit testing is a methodical approach to ensure that each unit (or module) works as intended and that it meets the requirements of its specification.

Below are some of the best practices for Unit testing your Java code.

Write Tests Before You Write Code

It may seem counterintuitive, but one of the best things a developer can do when writing unit tests in Java is to write them before you write any code. This way, you can think about what needs to be tested before you start coding. This can also help you from not having to write unnecessary code.

Determine Your Test Code Coverage

Java unit tests are evaluated based on their code coverage, which indicates the amount of code they cover. It is a useful tool for understanding how effective your unit tests are, and can help programmers improve them.

To figure out what percentage of the code in your entire application is covered by unit tests, you need to look at two things: 1 all the classes in your project and 2 all of your – or someone else’s – tests for all those classes.

Keep Your Unit Tests Small and Focused

When writing unit tests, one of the most important things to remember is to keep the unit tests as small and focused as possible. A developer’s tests should only test one specific thing at a time. This makes them easier to write and maintain, and also makes it easier to pinpoint which test is failing if a bug is found.

Read: Java Tools to Increase Productivity

Isolate Unit Tests from External Dependencies

When writing unit tests, it is best for a programmer to isolate their tests from external dependencies. Typical examples of external dependencies are databases, web services, and other software components that your code relies on.

Having all of these things running while you are trying to test your code can be a pain in the neck. By isolating unit tests, developers can write them quickly and easily without having to worry about starting up external resources. One way of isolating these external dependencies is by using mocks and stubs.

Implement Test Automation

Building your project with a build tool such as Maven or Gradle can make it easier to run your unit tests. Build tools can also be used to automate the running of your tests, which can save you time. You can leverage a continuous integration server to automatically run your unit tests every time your code is checked-in. This ensures that your tests are always up-to-date and helps to catch bugs early on.

Gradle Build Automation Tool
Example of Gradle Build Automation Tool

Our sister site, TechRepublic has a great article comparing Gradle versus Maven.

Avoid Testing Implementation Details

It should be noted that, when writing unit test methods, developers should refrain from writing code that tests implementation details. For example, if you are testing a method that calls another method, you should not be testing the details of how the second method is implemented; this can lead to tests that are brittle and difficult to maintain.

Mock External Dependencies

Mocks let you simulate behavior of components in your application to minimize resource consumption and reduce the time needed to run your test method. For example: You might want a mock user repository in order to simulate user interactions with a real user repository interface where none actually exist.

A programmer could also use mocks for testing web services — for example, testing how well an application handles errors returned from an HTTP request made via a REST API call. In order to isolate your unit under test (i.e., the object you are trying to test), you need to mock out all of its dependencies so that they do not actually call out to any external objects during testing.

For instance, if a programmer is writing a unit test for a Java object that uses an external web service, then in their test code they will want to replace that web service with a dummy implementation of it in order to prevent any real traffic from reaching the actual service. This is often done using mocking frameworks such as Powermock, Mockito, and so forth.

Use Assertions to Validate Expected Output for Unit Tests

When writing Java unit tests, assertions are used to validate the expected output. A developer’s code should not be verified by assertions; they should only be used to validate the expected results. If you find yourself using assertions in your test cases to verify that your code is correct, then this indicates that there is a flaw with how you are testing your application and probably means that test code coverage is low. Programmers should take advantage of proper assertions to verify whether the expected and actual results are identical.

Provide Meaningful Names to Test Methods

Test names should be descriptive, but they should not be too long. The name of your unit test method should describe the purpose of the test and the desired outcome. This helps developers to understand the intent of the test method easily.

Keep Unit Tests Up-to-Date

It is important to keep your unit tests up-to-date as your Java code changes. This can be done by regularly running your tests and making sure that they all pass.

Create Independent Code Tests

The first step in creating a suite of Java unit tests is to make sure they are independent of each other. Programmers should be able to run any test they want in any order and have it pass or fail in a reasonable amount of time. This allows developers to create a set of tests that can be run at any time and does not require waiting for other dependent unit tests.

The goal here is for your test suite to operate like an automated acceptance test for your code base; if one unit test passes, then everything passes. Keep unit tests in their own packages and away from production code. It is a good practice to keep them away from your production source code in general.

Check-in Only the Unit Tests That Have Passed

The first rule of unit testing is: make sure the unit tests pass before checking your Java code into a repository or a build system. This is because there is no point in writing code and then adding unit tests to it later if you are not going to run those tests regularly.

When you do this, you will find that your code will inevitably break when you make changes elsewhere — and then when someone else tries to build the project with these broken tests, they will be prompted with errors.

Final Thoughts on Java Unit Testing

Following good coding practices, such as using meaningful variable names and comments, will make your Java code easier to understand and maintain. This will make your – and other developer’s – life easier when writing unit tests for your code.

Unit testing, if done correctly by following the recommended best practices, can yield great results. By following these unit testing tips, programmers can make sure that their tests stay up-to-date and provide useful results when they run so they add value to your development life cycle and do not become an overhead to maintain over time.

Read more Java programming tutorials and software development tips.

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