Characteristic, Tools and Best Practices of Unit Testing

Testing in software development refers to the process of evaluating an application as it verifies that the software behaves as expected and there is no unexpected result of any action done on the application. In this article, we’ll learn about Unit Testing’s characteristics and how they help test the software.

What is Unit Testing?

Unit testing is a technique in which individual components of the application are tested in an isolated environment from other components.

1. This is done to ensure that the component or unit being tested functions properly independently.
2. It is generally referred to the smallest testable part of an application such as a search bar in the application or a simple filter function of an application.

Why is Unit Testing Important?

Unit testing is one of the most essential parts of testing due to the following reasons:

1. Early Error Detection: Unit testing helps us detect the error in the smallest unit of the program hence, prevents the programs from resulting in a larger bug that is complicated to understand. Also, bugs are less complicated to solve when they are in a smaller part of the code.
2. Saves Time: Through unit testing, we catch the bug in the earlier stage it prevents us from working on the wrong program and is easy to solve in less time. When in a unit a test case fails programmers can easily examine that part of the code and revert with changes.
3. Supports Agile Development: Unit testing supports agile development methods such as Continuous Integration(CI). It enables programmers to receive quick feedback and work on them quickly.
4. Enhancing the Quality of Code: Unit testing improves the code quality significantly as it ensures that the individual units are functioning properly. This further leads to fully reliable software.
5. Easy Maintenance: Units that are well tested through unit testing are easier to maintain and refactor. Units act like a safety net during code modifications, enabling developers to make changes without introducing new bugs.
6. Enabling Regression Testing: Unit tests serve as a baseline for regression testing, allowing developers to verify that recent changes made do not affect the existing functionality of the application.

Characteristics of Unit Testing

Unit testing which is testing of individual components of software has some major characteristics which are listed below:

1. Granularity

• Granularity refers to the level of detail at which something is examined or tested. In the reference of testing, it refers to the size of the code that is being tested.
• Unit testing targets a specific piece of code which allows the developer to examine and execute all possible test cases on that unit, making that unit free from any sort of bugs.
• The units targeted here can be functions, methods, classes, or modules depending on which programming language you have used. By targeting, individual units or components developers can pinpoint and address issues.

Example: If the search bar component is being tested as a part of unit testing then all types of input are given in the search bar such as searching without entering anything in the such bar, or giving some false input, etc. Then the output of these test cases is compared with the expected output and accordingly action is taken.

2. Isolation

• Isolation in unit testing refers to the practice of separating the unit of code from all the external dependencies such as network services, databases, etc. Unit testing has isolated units of code that are being tested.
• The code is isolated from its external services, databases, dependencies, or other components which work as an input supplier to the testing component or unit.
• The isolation is necessary to ensure that failure of some other component or dependency does not affect the efficiency of the unit being tested.
• Isolation promotes the behavior where the piece of code or the unit being tested in isolation behaves consistently and reliably in different situations.
• Isolation makes the debugging process simpler by narrowing down the scope of potential errors.

Example: Suppose for a shopping website a function is made to calculate the total sales for the day. We need to isolate this function as the testing of this function should not be affected by dependencies like the extraction of data of sold items from the database.

3. Quick Execution

• In unit testing tests are executed quickly because the tests are done on a smaller piece of code which allows the developers to execute all possible test cases quickly.
• Through quick testing, developers receive immediate feedback on code changes.
• This immediate feedback loop is essential for agile development practices.

4. Automation

• Unit testing should be made automated so that unit tests can be executed quickly and repeatedly.
• While manual unit testing is possible and developers often do it while writing programs on a large scale automation in testing is preferred as it has advantages like scalability, efficiency, and consistency.
• Automated unit tests ensure consistency in the testing process by executing the same set of tests repeatedly.
• Automated unit tests are very easy to integrate into the continuous integration (CI) pipelines.

Example: In modern software development, unit tests are integrated with CI pipelines using Jenkins and similar other tools.

5. White-Box Testing

• White-box testing also known as clear-box testing, is a software testing technique that focuses on understanding and examining the internal logic of the code that is being tested.
• Unit testing is seen as a part of white-box testing because prior knowledge is required for the implementation of the unit that is being tested.
• The quality management team generates test cases based on the understanding of the unit.
• One of the primary goals of white-box testing is to design test cases such that they check all the conditional statements.

6. Covering all Possible Test Cases

• As in unit testing a smaller portion of the code is tested, hence all the possible areas of examination are considered and tested properly.
• Unit test cases handle all edge cases and this gives a high probability that the code is bug-free.
• Coverage of all possible test cases ensures that conditional statements both true and false are tested.

7. Support for Refactoring

• Refactoring means making changes to the structure, or implementation of the existing code without altering its external behavior.
• The goal of refactoring is to improve code readability and performance.
• However unknowingly it can cause regressions in the codebase. This is where unit testing comes into action, through unit testing developers, run all existing test cases to ensure that all are working properly before making new changes.

8. Quick Feedback

• Unit testing helps us achieve the goal of quick feedback, which is important for programmers during the refactoring process.
• If some changes are made due to regression, an issue can be raised as soon as it is detected in unit testing and can be fixed.
• These quick feedback loops are crucial for programmers, especially during the refactoring process, where generally changes are made to improve the quality of code without altering its previous behavior.

Best Practices for Unit Testing

Some of the best practices for unit testing are:

1. Using Relatable Test Name: While performing unit testing the name used for the unit test should be chosen such that it gives us a bit of clarity about the feature that is being tested. This helps in understanding the purpose of the testing. Example: Suppose you have a simple function that adds two numbers so we can give the name to the unit as an addition.
2. Isolation Unit Testing: You must ensure that the unit test is independent of the other units so that some error in the other unit does not reflect in this unit. This reflects that the behavior of the unit is tested. Example: Suppose you have two units A and B and the output of unit A is the input for unit B. Then it should not happen that function A’s failure or wrong output would affect function B as in unit testing we are only concerned with the working of function B.
3. Evaluate Boundary Conditions: It is very essential to test boundary conditions in any piece of code for its efficiency. These test cases can be seen as a ground for errors like input validation, or some other basic error in code.
4. Frequent Unit Testing: Unit testing can be done frequently during development time so that the programmers can catch defects early. It is a very good practice to test with development, which includes a continuous CI pipeline to receive rapid feedback and automate test execution.
5. Include test cases that will lead to failure: Including test cases that will result in failure or error conditions is essential to help understand the behavior of the unit correctly in error scenarios and exception handling.

Tools and Frameworks for Unit Testing

There are a variety of tools and frameworks that are available for unit testing in different languages. Below are some of the popular tools:

1. JUnit: JUnit is a very popular unit testing framework for Java programming language. Junit allows a simple and effective way to perform unit testing for Java programs. Junit provides programmers with a set of assertions like `assertTrue`, `assertFalse`, `assertNull`, `assertEqual`, etc. which help to verify test methods. Junit supports continuous Integration practices.
2. JUnit Jupiter: JUnit Jupiter is the advancement of Junit, it is part of the JUnit 5 platform. It is a highly extensible unit testing framework for Java developers. JUnit Jupiter supports parallel execution of tests, allowing developers to run tests concurrently which helps in making the speed of execution faster. JUnit Jupiter can be easily integrated with Java 8 and its advanced version.
3. Mocha: Mocha is a JavaScript testing framework designed for both web browsers and Nodejs. Mocha has a simple and flexible syntax for writing tests. Mocha can be used in web browsers using a test runner like Karma, this helps developers to execute tests directly in the browser.
4. Pytest: Pytest is a flexible Python testing framework. It is known for its flexibility, simple usage, and rich features. Pytest supports parallel testing. It is also customizable through plugins.

Case Studies of Effective Unit Testing

Case Study 1

• Google, is one of the top companies and is leading the software development industry. Google is known for its simplicity, speed, and security features. Hence for such an organization, it is very important to use unit testing to save time and be efficient.
• Google Chrome’s code consists of millions of lines of code written in C++, JavaScript, etc. and to ensure the reliability of the browser, it has a comprehensive unit testing strategy.
• Unit tests are written for individual components so that the developer can rectify errors, if any. Its build and release process includes automated execution of unit tests which are a part of the continuous integration(CI) pipeline.
• As Google is a very complex software hence having a detailed testing strategy is essential to maintain software quality. Google Chrome has unit tests designed to evaluate the behavior of specific units in isolation.

Case Study 2

• Facebook, is a prominent social media platform, which keeps in mind the importance of unit testing in its software development lifecycle.
• Facebook’s codebase is complex and requires proper testing to maintain reliability. Unit tests are integral to Facebook’s development workflow, allowing developers to test and evaluate individual components that are isolated from other components.
• Unit tests are easily integrated with Facebook’s development workflow, enabling programmers to validate their code changes through automated tests. These tests help developers detect errors or unexpected behavior in individual components very early in the development phase.
• Through effective unit testing practices, Facebook ensures the stability and performance of its platform which enhances user experience and also increases the reliability of users.

Conclusion

Unit testing is a very important part of software development which involves testing a single unit of code that is isolated and free from dependencies. It helps detect errors at the earliest possible and is characterized by granularity, isolation, quick execution, automation, white-box testing, quick feedback, and support for refactoring. Using them leads to effective unit testing that can be done across different programming languages.