What is unit testing?
Unit testing is essential in the software development life cycle. It’s a detailed process, where each tiny piece of application code is tested to make sure it works. To create unit tests is to set the foundation for all the subsequent testing stages. A unit test shapes the overall performance of the final software.
This article covers unit testing, its best practices and tools, and advanced techniques to build quality software.
Importance of Unit Testing in SDLC
Why run unit tests?
At the heart of any good software is a set of well-written unit tests, built and executed during the development process. Not just a task to be ticked off, it’s a strategic approach to automated testing, to make sure every piece of code aligns with the application's goals.
Unit testing is the first line of defense against bugs, catching them early, when they're cheapest and easiest to fix. As a tester/developer, if you follow test-driven development (TDD)—writing test code before the application code—then unit testing is a must.
Why unit testing is essential
By catching bugs before they become big issues, automated unit testing not only improves code quality but also makes the software development process smoother and more efficient. A unit test helps to:
- Verify functionality
- Ensure code is correct
- Understand the code base
- Instill confidence that the application will work
How unit tests work
Unit tests follow a process that goes through each code block. Below are some of the techniques for automated unit testing:
Writing unit tests
Writing a unit test involves three steps:
- Arrange: Write test cases and test data for test automation and choose the relevant testing environment.
- Act: Run the unit test code and see how it works.
- Assert: Compare the actual behavior with the expected result to verify.
Running unit tests
After writing unit tests, you need to run them to see the results. This can be done using a unit testing framework that uses automated testing. Automated testing frameworks group the test cases into a test suite and provide a detailed report of the results.
Zoho QEngine has specialized and user-friendly features to make testing easier for developers and testers, so they can focus on the code that matters.
Types of unit testing
There are two types of unit testing—manual and automated. Each has its own advantages and disadvantages, and understanding them will help developers and testers choose the right approach for their testing needs.
Manual unit testing
In software development, manual testing is testing the application features, data validations, integrations with third-party tools, and more, for anomalies. Testing a few use case scenarios is possible with manual testing, but testing multiple code units is a time-consuming process, prone to human error.
Automated unit testing
Automated unit testing uses automated testing tools to test huge volumes of test cases both faster and more efficiently. This approach allows you to run tests repeatedly and consistently and catch bugs as soon as they appear.
Today, test automation frameworks are the preferred choice because of their speed and reliability.
Unit testing vs other testing methods
While unit testing is part of software quality assurance, it’s not the only testing method in a developer’s toolbox.
To understand unit testing better, it’s important to know how it fits in with other testing approaches, like integration, functional, and regression testing, to ensure overall software quality.
Unit testing vs integration testing
Unit testing looks at the smallest parts of the system, and integration testing looks at how these parts work together. While unit tests ensure individual components work as expected, integration tests ensure the combined functionality of these components meet the system requirements.
Unit testing vs functional testing
Unlike unit testing, functional testing takes a wider view, testing the software against all the user requirements and specifications. Functional testing ensures the software works as a whole and does what it’s supposed to do.
Unit testing vs regression testing
Unit tests are used to test individual components, while regression tests protect against new changes that might break existing functionality.
Unit testing techniques
To become proficient in unit testing, you need to know various techniques, with each looking at the software application from a different angle. From white box testing, which tests internal logic, to error-based testing, which tests for potential errors, knowing them will help you create robust and effective unit tests.
White box testing
Development teams witnessed a huge increase in developer productivity and development velocity.
Black box testing
It is easier for the quality assurance (QA) teams to automate continuous testing and multiple regression tests with feature flags.
Error-based testing
Improved collaboration between teams contribute to overall improvements in product management.
Unit testing tools
The right tools can make a big difference in unit testing, making the process faster and better. Some popular unit testing tools for different programming languages and platforms are:
- Zoho QEngine: A no-code, low-code, pro-code unit testing tool
- JUnit: For Java
- Mocha: For JavaScript
- PHPUnit: For PHP
- NUnit: For .NET
- Pytest: For Python
Zoho QEngine
Zoho QEngine is a test automation tool that can be used for unit testing applications. It has a no-code recorder, low-code builder, and pro-code editor, to help you build test cases easily. QEngine also has a manual editor for manual unit testing.
Zoho QEngine is equipped with single-window cross-platform management, which helps in the unit testing of applications for multiple platforms, be it web, Android, or iOS.
Since QEngine supports data-driven testing, data for unit test cases from different files, such as XLSX, CSV, and more, can be incorporated into test case scripts for more efficient testing.
Depending on the complexity of the features and testing strategy, multiple unit test cases can be segregated into individual modules or placed in different standalone projects. Test cases can be scheduled and run on the cloud, or via local machine or tunneling. With its reporting feature, the unit test case results can then be easily analyzed.
JUnit for Java
JUnit has a simple framework for test-driven development and helps to maintain the consistency and stability of Java code. It’s a tool that helps developers write tests efficiently in Java.
NUnit for .NET
For the .NET framework, NUnit has all the features to write and run unit tests. It supports parallel testing and data-driven tests.
Mocha for JavaScript
Mocha is flexible and extensible for JavaScript and Node.js applications, accommodating all testing needs. It’s a proof of the dynamic nature of JavaScript development, with the flexibility to keep up with ever-changing web technologies.
Unit testing best practices
By following these best practices, developers can make their unit tests more effective, maintainable, and scalable.
Write readable tests
Readable tests are the hallmark of maintainable software, as both a check and documentation for future developers. By naming tests descriptively and structuring them clearly, developers can make sure their intent is understood and tests can be relied upon for years to come.
Create deterministic tests
Creating deterministic tests is like building a fortress—it’s about making sure every test run produces the same result under the same condition. By controlling external dependencies and environment variables, developers can write tests that are robust and reliable, which is a benchmark for code quality.
Unit testing automation
Automating unit tests allows you to:
- Run tests frequently and quickly, as part of continuous integration
- Save time
- Reinforce the codebase with each change
- Ensure confidence in the software
Other unit testing strategies
In the more advanced world of unit testing, you'll find methodologies and practices that improve the quality and security of the software. From the discipline of test-driven development(TDD) to the watchful eyes of security testing, these are some advanced unit testing strategies:
Test-driven development (TDD)
Test-driven development (TDD) isn't just a testing practice—it’s a design philosophy that shapes the way software is built. By writing tests first and code second, developers can make sure their software isn't only functional but also well-designed and maintainable.
Continuous integration and unit testing
Continuous integration (CI) and unit testing are a perfect pair. CI builds and tests the code and gives immediate feedback on software health.
When unit tests are part of the CI pipeline, they become a tool to maintain code quality throughout the development life cycle.
Security testing with unit tests
Including security in unit testing is a proactive approach to secure the software from threats. By including security checks in the testing process, developers can catch vulnerabilities early and harden the software against attacks, so security isn't an afterthought but a part of the development process.
Real-world examples
Unit testing is most valuable when used in real-world scenarios. From mobile development in Android to web applications in Angular and React Native, unit testing is a tool that fits many platforms and languages.
Unit testing in Android
In the world of Android development, unit testing is crucial to ensure apps are reliable across many devices. By using both local and instrumented tests, developers can test their apps thoroughly, so every function works as expected, regardless of the environment.
Unit testing in Angular
The Angular testing framework gives developers the tools to build reliable web applications. By using TestBed and other utilities, unit tests in Angular can simulate component behavior and validate interactions, so every part of the application works as expected.
Unit testing in React Native
The React Native approach to unit testing shows the framework’s commitment to building user interfaces that are robust and responsive. By using Jest and the React Native testing library, developers can write tests that simulate user interactions and validate component functionality, so apps work well across different platforms.
Conclusion
Unit testing isn't just a technical requirement—it's an essential process in the software development life cycle. By using the techniques, tools, and practices above, developers can make sure their code is functional, resilient, and secure.
Frequently asked questions
What is a unit in unit testing?
In unit testing, a "unit" means the smallest testable part of the software, individual function, method, or procedure that can be tested independently for correctness.
How is unit testing different from integration testing?
Unit testing tests individual components in isolation. Integration testing tests how different components work together as a whole to perform their intended tasks. Both are complementary to ensuring software reliability.
Why automated unit testing over manual unit testing?
Automated unit testing is preferred over manual testing because it’s faster and less prone to human error. It runs tests automatically, saves time, and ensures consistency.
Can unit testing improve software design?
Yes, unit testing, especially when combined with TDD, leads to better software design, by making developers think about how components will be used and resulting in cleaner and more maintainable code.
How unit testing contributes to software security
Unit testing contributes to software security by allowing developers to include security checks, catch vulnerabilities early in the development process, and make security part of the process. This proactive approach prevents security issues instead of addressing them as an afterthought.