Unit testing is essentially the process of isolating the smallest functional components of your code and making sure they’re working properly. It’s a critical part of the development process and, when implemented continually throughout development, helps to build a solid foundation for scalable applications.
It has the benefit of being cheap and fast, and by following our unit testing best practices, it doesn’t have to be a difficult task. So in this article, we’re going to take a look at what unit testing is, why it’s important and how to go about it.
As part of developing software, there will be a lot of changes to code. Whether these will be adjustments or additions, essentially, the product will be different from before the change. Whenever such a change is made, it’s useful to run a test to make sure that it hasn’t broken something and that everything still runs in the way it did before the alteration. This is the concept of regression testing.
There are a few ways to implement regression testing. Focusing on the application as a whole is called system testing. Regional testing is narrowing the scope of the code flow between affected components. Testing individual components of code themselves, or units, is called unit testing.
These units can be isolated by writing tests that are only concerned with the units themselves. Whether your affected unit is being relied upon or affecting other systems when it’s in action, the unit test will not be concerned with these interactions and will only focus on the unit’s function itself.
How Unit Testing Works
So, unit testing is a useful way to make sure an alteration hasn’t affected the program’s functionality. This can be done manually for generalized testing methods and small applications, but as the application grows, it becomes more important to have automated tests and tests that test the finest grained logic of the smallest components of the application.
In order to isolate these small components, they need to be encapsulated in memory. Creating simulated systems for the unit to input from and output to is, in this case, called ‘mocking,’ and it’s how unit testing is performed when the unit has external dependencies.
Isolating units in this way allows tests to be written specifically to challenge their functionality, independent of other factors. Usually, deterministic tests are used so that the output should always be the same if the component is working as it should, no matter how many iterations it is tested with.
Why and When to Use Unit Testing
In an application, it’s better to have one component to do one thing. This is the essence of modular code development. With a complex application, full-scale testing displays the results of innumerable variables, and it’s impossible to accurately determine exactly what’s working and what isn’t. Having modular code simplifies the testing process.
Suppose you can isolate specific code components and run individual tests on their functionality. In that case, you’re able to assess subsets of the application on their own and identify hidden bugs much more precisely.
Therefore, besides making bug identification clearer, unit testing promotes a robust product design and inspires much more modular production of applications.
Unit testing should be done continually – not simply at the end of production. By the completion of each stage of development or after every significant change, unit testing should be implemented to ensure the architecture is robust; this will also aid in scalability in the future.
To keep things relatively simple, it’s good to follow a series of key practices. So here we’re going to look at some of the best unit testing guidelines.
Unit Testing Best Practices
- Run them early and often
One of the best ways to improve the quality of your development is by making unit testing part of the build process of your software. Tests need to be factored into your continuous integration approach, so they’re not overlooked, and this can also prevent countless bugs from slipping through along the way.
It’s a lot more time-consuming and complicated to test for bugs at the end of a sprint, and since unit tests are cheap and fast, they can make up the majority of your testing. It’s even recommended that unit tests make up 70% of your testing strategy.
- Remove Redundancy
Following a concept called ‘Don’t Repeat Yourself’ (DRY) is a way to improve efficiency by writing code that isn’t duplicated. When it comes to testing, this practice cuts down on redundancy by creating a single representation for any piece of system knowledge.
The downside to the DRY process may be that there isn’t such an obvious description of code to make it easy to see with a glance what’s happening in the text – this is where DAMP comes in.
- Name your tests effectively.
While it may sound like the antonym of DRY, DAMP, or Descriptive and Meaningful Phrases are actually a complement to the DRY approach, at least in terms of unit testing. This principle reduces the time needed to read and understand the code, so there are obvious benefits to testing that come with that.
DAMP approaches allow you to label steps with exactly what they do by describing them with their purpose and relevance at the time of writing. While DRY allows you to express how an object is working, DAMP will allow you to easily see what it’s doing.
Both DRY and DAMP can allow for code that’s easier to maintain and, therefore, more maintainable unit testing.
- Use deterministic testing
While false positives and negatives can arise, deterministic unit testing should demonstrate repeated, exact outcomes when given identical inputs. Using deterministic testing will bring more confidence in the results of your unit testing, as non-deterministic tests give essentially arbitrary results.
To make sure your tests are deterministic, they cannot rely on any other test cases or external dependencies – this means they have to be entirely isolated.
- Follow AAA
Using a pattern of Arrange, Act, and Assert is common in unit testing and breaks the process into three stages:
- Arrange – This step initializes objects, sets up any mocks and expectations you might be using, and sets up the test itself.
- Act – Then, with the arranged parameters, the Act stage invokes the tested method.
- Assert – Finally, the verification of the test involves making sure the action of the method under test produced the desired result.
This isn’t the only way to run unit testing, but it’s a popular pattern that breaks it into simple steps, structures your functional test cases, and is an excellent general guideline.
While automating unit tests might begin as an overwhelming endeavor, ultimately, it’s going to save time, improve accuracy, and increase throughput enormously. Automation should be adopted as soon as possible to make the best of its time-saving investment over the long run.
Automation also improves coverage for these reasons, and since unit testing involves breaking down your code into its smallest components, without automation, this becomes very difficult as applications grow larger.
Unit testing doesn’t have to be complicated; working it into your build process pays for itself in more efficient code, fewer bugs, and stronger frameworks.
Writing deterministic tests with as little redundancy as possible, describing their function for easy access, and running them through AAA as often as possible are the keys to successful unit testing. Automation should be implemented as early as possible, so it’s not hard to keep up with a growing platform.
Follow these unit testing best practices, and you’ll immediately improve the power of your unit tests and, therefore, the running of your software.