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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. The process is repeated at every software development stage.
Unit tests are particularly important in developing applications and the tests can be valuable not only during development but also in post-release maintenance.
Added to the requirements, unit testing is done during the development phase of an application by the developers. This article will look at what is unit testing 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 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.
Unit tests can be written and executed by the developer and can be automated via a build process. Unit tests provide a quick way to verify that the component’s design is sound and meets its specification.
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.
A unit test launches a small part of the application independently of the other ones and verifies if it behaves as expected.
There are three phases in a unit test:
- Arrange — setting up the testing objects and initializing a part of the application we are going to test (system under test or SUT)
- Act — applying stimulus to the SUT (usually by calling a method)
- Assert — observing the behavior of the system.
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 a system.
Why do you need unit testing?
Unit testing is an important factor for software developers to get their work done. It is important for developers to follow unit testing guidelines. When developers choose not to follow these guidelines, they might end up with a high-cost defect fixing during System Testing, Integration Testing and even Beta Testing after the application is built.
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.
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. There are a few best practices that you can follow to improve your unit testing.
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 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 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.
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.
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 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. We hope that you found it informative and that it helped to clear up any questions you may have about what is unit testing in software testing. If you have any questions or concerns, please contact us anytime!