Part 1: Introduction to Unit Testing (with examples)

Unit testing is a software testing technique in which individual units or components of a software application are tested in isolation from the rest of the system. The goal of unit testing is to validate that each unit of the software application is working as intended. A unit is the smallest testable part of an application, such as a function or a method.

For example, consider a simple function that takes two integers as input and returns their sum. A unit test for this function would involve passing in specific input values and then checking that the function returns the expected output. This ensures that the function is working correctly and that any changes made to the function dont break its expected behavior.

Unit testing is typically done by developers as part of the development process, and its usually automated. This means that once a unit test is written, it can be run repeatedly without the need for manual intervention. This is important because it allows developers to catch bugs early in the development process, before they make their way into the final product.

For instance, if a developer changes the function to subtract the two integers instead of adding them and runs the test, the test would fail, alerting the developer of the mistake. This helps to prevent bugs from being introduced and ensures that the software is working correctly.

Unit testing also provides a way to ensure that the code works as intended and that new changes dont break existing functionality. This is achieved by writing tests for each unit of the code, and running them every time a change is made. If a test fails, it means that something is wrong and needs to be fixed.

Unit testing is also an important tool for improving the design of the code. By writing tests for each unit of the code, developers are forced to think about how the code is organized and how it can be made more modular and testable. This can lead to a better overall design and a more maintainable codebase.

Unit tests also serve as living documentation for the code. They provide examples of how the code is intended to be used, making it easier for other developers to understand and maintain it. This is especially important for large codebases or projects with multiple developers.

Example Use Case:

Consider a software application that manages employee information for a company. The development team is tasked with building a feature that allows managers to view and edit the personal information of their employees. The team decides to implement unit testing as part of the development process to ensure that the feature is working as intended.

The team writes several unit tests that cover different scenarios, such as adding a new employee, editing the information of an existing employee, and searching for an employee by name. During development, the team runs these tests frequently to ensure that the code is working as intended.

As the development progresses, the team makes several changes to the code, but thanks to the unit tests, they can be confident that the changes havent introduced any bugs. Once the feature is complete, the team runs the tests one final time, and all the tests pass.

The company launches the feature, and it functions as expected, allowing managers to view and edit the personal information of their employees quickly and easily. Thanks to unit testing, the team was able to catch and fix issues early in the development process, which saved time and resources in the long run.

In summary, unit testing is a software testing technique that helps to catch bugs early in the development process, ensure that the code works as intended, improve the design of the code, and serve as living documentation for the code. Unit testing is an essential practice that every developer should be familiar with, and it is especially useful when developing complex systems or working on large codebases.

Series: Why unit testing is important ? All about unit testing

Part 1: Introduction to Unit Testing

Part 2: Catching Bugs Early

Part 3: Ensuring Code Quality

Part 4: Living Documentation

Part 5: Continuous Integration and Deployment