What Is Unit Testing?

What Is Unit Testing: Introduction

Unit testing is a form of software testing used by developers to ensure that individual units or components of the software are tested. This process, often involving automation unit testing, is repeated at every stage of software development, making it a critical step in maintaining code quality and reliability.

Unit tests are particularly important in developing applications, and the tests can be valuable not only during development but also in post-release maintenance. Automated unit testing allows developers to run tests quickly and frequently, ensuring that new code changes do not break existing functionality.

When diving into unit testing, begin with small, simple tests for individual functions or components. This will help you get comfortable with the process without feeling overwhelmed. Remember, the goal is to test one thing at a time.

Mikhail Bodnarchuk

CDO, ZappleTech Inc.

Added to the requirements, unit testing is done during the development phase of an application by the developers. This article will look at what unit testing is in software engineering, how it is implemented, and the importance it has in the development phase. We will also give a brief overview of the tools commonly used for unit testing, including those that support automation unit testing, and share our experience regarding unit testing best practices.

What is unit testing, and why do you need it?

Unit testing is a software development practice whereby a developer tests the smallest possible piece (such as a class, function, or method). This is important because it enables developers to test units in isolation from the rest of the software and identify the low-level causes of bugs. Unit testing is often a necessary prerequisite to integration testing.

Automation unit testing takes this process further by leveraging tools and frameworks to run tests automatically, which significantly speeds up the testing cycle. Automated unit testing ensures that every change to the codebase is validated against the existing functionality, catching regressions early. This approach not only improves code quality but also enhances developer productivity by providing immediate feedback on code changes.

Furthermore, automation unit testing allows for continuous integration and continuous deployment (CI/CD) practices, where tests are run automatically whenever new code is integrated into the project. This helps maintain a stable codebase and supports rapid development iterations. Incorporating both automation unit testing and automated unit testing into the software development lifecycle helps teams deliver robust and reliable software while reducing the time and effort spent on manual testing.

How does it work?

Unit testing isolates the smallest testable component of a software application, tests that component, and ensures that the component works as expected. By testing only the smallest component, developers can be confident that it is working properly. Additionally, unit tests are executed within seconds and are easy to perform.

Automation unit testing streamlines this process by using tools and frameworks to automatically run unit tests without manual intervention. This not only saves time but also ensures that tests are consistently executed every time code is modified. Automated unit testing involves setting up a test environment where each unit test can be triggered automatically as part of the development workflow, often integrated into the continuous integration and delivery pipeline.

A unit test launches a small part of the application independently of the other ones and verifies if it behaves as expected. With automated unit testing, this process is repeated consistently, allowing developers to catch issues early and frequently. Automation unit testing provides a more reliable and scalable approach to verifying software components, making it an essential practice in modern software development.

There are three phases in a unit test:

1. Arrange — setting up the testing objects and initializing a part of the application we are going to test (system under test or SUT). This phase is crucial in both automation unit testing and automated unit testing, as it ensures the environment and dependencies are correctly configured before proceeding.
2. Act — applying stimulus to the SUT (usually by calling a method). During automated unit testing, this phase involves executing the specific actions or methods that need to be validated, allowing for consistent and repeatable test runs.
3. Assert — observing the behavior of the system. This stage checks whether the outcome aligns with expectations. In automation unit testing, assert statements compare actual results against expected values, helping to confirm the correctness of the SUT.

The Arrange-Act-Assert stages are simply called AAA. If the actual behavior matches the one described in the specification, the unit test passes. Otherwise, it fails, indicating a problem somewhere in the system. Employing automated unit testing techniques allows for these processes to be streamlined, reducing manual intervention and enhancing the overall reliability of testing outcomes..

Why do you need unit testing?

Unit testing is an important factor for software developers to get their work done efficiently and effectively. Incorporating automation unit testing allows developers to quickly identify issues early in the development cycle, making the overall process more efficient. It is important for developers to follow unit testing guidelines and best practices to ensure the quality of their code. When developers choose not to follow these guidelines, they might end up with high-cost defect fixing during System Testing, Integration Testing, and even Beta Testing after the application is built. Automated unit testing helps in reducing these costs by catching defects early, thereby improving code reliability and maintainability.

Unit tests help catch the bugs at the lowest level of the software and to fix it quickly and cheaply. But this is not the only advantage of applying unit tests:

1) Unit tests serve as a basis for documentation

Unit tests serve as a basis for documentation. They can give you a basic idea of what each function is doing and what the end result is. Unit tests are a good way to keep track of what is happening in the code, and they take a lot of the guesswork out of what the code is doing. They also serve as a way to document the code to help people understand it.

2) Reusability of scripts

When you write unit tests, the individual modules of a product have the opportunity to be tested in a contained environment. This means that the code is more reliable, and therefore reusable. Unit tests are also a great way to ensure that the code is written in a clean and understandable way, which can help in the future.

3) Increasing test coverage

Unit testing is a powerful method for improving code quality and increasing development efficiency. However, it can be difficult to know which areas of code have been tested and which have not. A popular method of testing is the use of code coverage tools to determine the percentage of code that has been exercised by tests. These tools are able to graphically display the code sections that have been exercised by tests and the sections that need to be tested.

4) Reducing code complexity

An important part of writing unit tests is to test the code for its complexity. The more complex the code, the more difficult it will be to write unit tests. When the process becomes cumbersome, it signals that the code might be overcomplicated, too. But without unit tests, you have no way to objectively answer whether your code works or not.

Automation unit testing and automated unit testing are your best friends. They save time, catch bugs early, and help maintain code quality. Invest time in setting up a good automated testing framework; it will pay off in the long run.

Sergey Almyashev

COO, ZappleTech Inc.

Unit testing best practices

Unit testing is an essential part of any software system, and it’s important to always try to find ways to make your unit testing better. Incorporating automation unit testing into your development process can significantly enhance efficiency and accuracy, allowing developers to quickly identify and fix bugs. There are a few best practices that you can follow to improve your unit testing, such as writing clear and concise test cases, ensuring each test focuses on a single functionality, and regularly refactoring your tests to keep them relevant and effective.

One crucial aspect of improving unit tests is to use automated unit testing tools, which can help streamline the testing process and provide quick feedback on code changes. Automated unit testing enables continuous integration and continuous delivery (CI/CD) pipelines, ensuring that new changes do not break existing functionality. It’s also beneficial to maintain a high level of test coverage by testing edge cases and error conditions, as this improves the robustness of your software. Finally, running tests in isolated environments to avoid dependencies on external systems ensures that your tests remain consistent and reliable. By following these best practices, you can optimize your unit testing strategy, making it a powerful tool for delivering high-quality software.

1) Fast tests

When you write unit tests, you want to make sure that they are fast. If your tests are slow, developers won’t run them as often as they should because they’re time-consuming. That defeats the entire idea of unit testing. Things like using a multithreaded environment, caching and batching are ways to make your unit tests run quickly without having to put in a lot of effort.

2) Simple tests

Your unit tests should be as simple as possible. You should keep your unit tests with low cyclomatic complexity. This is a code metric that indicates the number of possible execution paths a method can take. A piece of code with lower complexity is easier to understand and maintain.

3) Readable tests

Tests don’t have to be complicated to be effective. You should keep your tests simple, clear, and easy to read. Developers will be more likely to understand and follow your tests if they are easy to read.

4) Deterministic tests

Determinism is a concept in programming where an algorithm is guaranteed to produce the same result if executed with the same input. All variables and states of the program must be the same and the order of execution must be the same. This is one of the best practices to follow when writing unit tests. When the code under test has been changed, the unit tests should be re-run. This ensures that the unit tests are run in a deterministic fashion.

Tools for unit testing

Unit testing tools are used to create testable code that enables developers to write code more quickly and to make sure that the code works as expected. Let’s see, what is unit testing, with examples of commonly used tools.

JUnit

JUnit is a software testing framework that provides a set of core functionality integrated into one library. It is designed to facilitate writing and running unit tests. The framework is meant to be used in conjunction with the Java programming language.

JUnit is based on the idea of test-driven development where a unit test is written before any source code, and then the source code is written to pass the unit tests. The framework simplifies this process by providing an abstract layer that handles the setup, execution, and clean-up of tests. It also allows developers to run tests in parallel to improve speed.

It gives developers the ability to build a test suite that is incrementally built to measure progress and detect unpredicted side effects. JUnit tests can be run continuously and provided immediately. The JUnit test progress bar is typically green but turns red when a test fails.

TestNG

TestNG is a next-generation open-source testing framework. TestNG is inspired by JUnit, but it is more powerful when it comes to controlling the flow of your program. The framework architecture helps us make tests more structured and provide better validation points.

It is an object-oriented framework that gives the developer an easy way to write unit tests for Java. TestNG is easy to use and comes with a lot of features that make writing tests easier, such as test grouping, test sequences, annotations, and parameterization. This makes it easier to manage large projects.

In addition to these capabilities, TestNG also borrows from Java Annotations. This means that TestNG can also show you how to use this new feature of the Java language in a production environment.

Jest

Jest is an open-source testing framework built on JavaScript, designed majorly to work with React and React Native based web applications. Jest can be used to validate almost everything around JavaScript, especially the browser rendering of web applications. It provides a robust and simple API for running tests across multiple environments and supports test-driven development.

You can use Jest as a complete testing tool, but it is also compatible with Mocha and Chai, which means that you can use it to test any JavaScript application. It provides an assertion library and a mocking library for testing. Additionally, you will have an easy way to test JavaScript Library Projects such as AngularJS, Vue JS, Node JS, Babel and TypeScript.

The framework also includes some advanced features like the ability to auto mock modules, setup coverage thresholds, module mappers. It also has rich documentation, a large user community and supports multiple projects in the same runner and customer resolvers like Babel and Webpack.

Mocha

Mocha is a JavaScript test framework that can be used to test both client-side JavaScript code and Node.js server-side code. It is written in CoffeeScript and can be used with the browser. It is also compatible with any JavaScript engine. Mocha supports functional, asynchronous, and synchronous programming.

Its API is easy to use and can be extended or modified, making it suitable for a wide range of testing scenarios. The tool will then execute all the tests that you have created using the describe function and then report back how the result of the test to your console, terminal or a test report.

Mocha tests run serially, allowing for flexible, accurate reporting, and mapping uncaught exceptions to the correct test cases. Mocha has a rich set of features for test automation, including multiple testing frameworks, assertion helpers, a unified, pluggable API, and more. It also cleans the state of the software being tested to ensure that test cases run independently of each other.

Pytest

Pytest is a testing framework for Python. It is the most popular Python tool for writing, testing, and scaling to support complex testing for applications and libraries. It is easy to write, so it is easy to test, and it scales to support complex testing for the applications and libraries.

With this framework, you can write plugins that can be run in different ways, run once, or run continuously. They give more freedom to software developers in terms of testing their code. It is easy to use and integrates with the natural workflow of Python developers.

Pytest can be used by development teams, QA teams, independent testing groups, individuals practicing TDD, and open source projects. It can also be extended with plugins to handle testing database applications and test coverage reporting.

What Is Unit Testing: Conclusion

We hope you enjoyed our article about unit testing. Unit testing plays a fundamental role in software development, providing the foundation for ensuring the reliability and quality of individual components. By incorporating automation unit testing, developers can run tests more frequently and consistently, catching issues early in the development cycle. Automated unit testing not only saves time but also improves accuracy by eliminating the potential for human error during manual testing.

Don’t be afraid of tests failing—that’s what they’re there for! Failing tests are your early warning system, giving you the chance to address issues before they affect the larger codebase. Embrace the process: fail fast, fix fast, and move forward confidently.

Mykhailo Poliarush

CEO, ZappleTech Inc.

Automation unit testing allows developers to quickly validate that each piece of code behaves as expected, making it easier to identify and fix bugs before they escalate into bigger problems. This approach supports continuous integration and continuous deployment (CI/CD) pipelines, contributing to a more efficient and agile development process.

Whether you’re new to unit testing or looking to deepen your understanding, embracing both automation unit testing and automated unit testing can significantly enhance your software’s stability and performance. We hope that you found this information informative and that it helped to clear up any questions you may have about what unit testing is in software testing. If you have any questions or concerns, please contact us anytime!