Unit testing is a way to test small units of code. You usually do it in the development process, long before releasing the code to customers. You can also do unit testing to check if the code in a new update breaks any existing functionality in a program.
Some people in the software industry say that unit testing is a waste of time and it’s not worth the upfront investment.
They argue that there’s no evidence that unit testing increases software quality or developer productivity. Others say that unit testing will help developers understand their code better and develop more secure programs.
Unit testing is not a waste of time:
- It will ensure that each unit of code runs as designed and is independent of other units.
- It will help developers understand their code better, especially new and unfamiliar code.
- It will find bugs and errors early in the development process.
This article will discuss why unit tests can be important for your application and how you can implement them with ease.
What is unit testing?
Most software applications are not one-time efforts. They are often patched, modified, and upgraded with code from many different developers.
Unit testing ensures that each code unit does what it says it will do for you. Both now and in the future. Besides confirming correctness under normal conditions, they often give immediate feedback on logical bugs occurring within your system logic flow before they become difficult to detect (and fix).
Unit testing often happens before the software is complete, during the development phase.
Besides unit tests, there are many different types of tests. For example, you can perform integration testing, which also happens throughout development. With the integration test, you check that a feature as whole works as expected.
Is unit testing a waste of time?
Unit testing may not be the only way to ensure software quality, but it is necessary.
The fundamental principle of unit testing is that developers should test each part of the system in isolation. A basic unit test will assert given some input against an expected output and will check for exceptions. This allows every app component to be tested alone, without depending on anything outside themselves or any other parts within the software application.
With this kind of purity, it’s possible to fully understand all the responsibilities the unit has. You can also ensure there are no error-prone modules or branches in an application codebase.
But unit testing alone is not enough. You should do testing at the unit, integration, system, and acceptance levels. Different levels of testing represent the testing pyramid.
How does it help developers?
There are different ways that good unit tests help developers: they create modular code, improve code coverage, and help the developer to understand the code better.
Create modular code
By writing a unit test, there is a greater chance that you will create a more modular code. Because unit testing focuses on small units of production code, you will naturally try to make small testable pieces of code. This means you can test each unit in isolation. When you write a unit test case for a small piece of code, it also becomes easier to read and maintain.
Writing unit tests forces you to create smaller classes and combine them using dependency injection.
Improve code coverage
The second benefit of unit testing is that it improves code coverage. Code coverage (also sometimes referred to as test coverage) is a test metric that tells you how much of your code base is tested with automated testing.
In practice, this means that unit testing and test driven development (a popular agile software development technique where unit tests are used to drive code design) result in higher code coverage.
Unit testing has a real impact on test coverage: you can use unit tests to “fill the gaps” in your existing test suite and create new unit tests when adding new functionality to your application.
Find bugs early in the development process
Unit tests find bugs early in the development process because it is easy to test on a small scale and see if something breaks.
The unit test will signal a failure when there are problems with the code. Developers can then go back and fix these errors before they release the code to customers.
When you correctly perform unit testing, you will have a more accurate model of what you are developing.
Unit testing can also test for some issues that aren’t as easy to catch through manual testing. For example, some issues may only appear when you use a particular language construct or scenario (e.g., concurrency issue). A solid set of unit tests for all of your business logic can save significant amounts of time during software development.
Understand the code better
Test code can also serve as a great technical documentation of your production code. They are especially valuable when dealing with legacy code: highly complex code that someone else wrote a long time ago. They can save you from making costly mistakes and introducing bugs.
By writing unit tests, you gain an understanding of the unit you’re testing. But also, through unit tests, you can show the unit’s behavior to other developers. As a result, you can help yourself and others.
However, the unit test code itself needs to be well written.
What are the consequences of not unit testing?
The consequences of not unit testing are that you have no verification of the code. You aren’t aware of the possibilities in your code or what it does, so when problems arise, you won’t be sure about how to fix them. You also won’t be able to prove that the issues are gone.
You can say, “It works on my machine!”, but you never can be 100% sure.
What are the disadvantages of unit testing?
Unit tests are great. However, they are not a silver bullet and won’t catch all bugs.
Writing tests takes time. It’s even worse when you need to trace through legacy code or when the framework does not make it easy to write tests.
Many times test code becomes bloated and hard to maintain.
I’ve seen projects with piles of unit tests, but they used too many mocks. And that resulted in tests that test the implementation detail instead of testing the observable behavior. However, nobody realized it until someone wanted to change something in that part of the system. Then, every change resulted in multiple failing tests.
When testing slows you down more than it helps, then you stop writing tests at all.
Conclusion
Unit testing is a great way to ensure that your production code behaves as you intend.
You can achieve it by writing test cases using a unit testing framework like NUnit, MSTest, and xUnit. In addition, automated tools are often used because they save time and provide better feedback than manual tests.
Unit testing should be part of any software development process, but it is crucial for those who work with C# because .NET projects can quickly grow in size and complexity.