Recently I read this great article on the DZone website called The Business Case for Unit Testing by Erik Dietrich In this article, he sets out six reasons why Unit Tests should be considered as a serious business need and what benefits they bring to a business.
Two of the points Erik makes I feel are extremely important as to why Unit Tests are so a crucial part of an application. One, The Test Suite Reduces Deployment Risks, by having a good set of tests that can be run when the application is about to be deployed. There is less risk that issues will occur during this deployment phase, making the application deployment smoother and getting the application to your users quicker.
How do Unit Tests Reduce Deployment Risks?
As an application is being developed, your development team will continue to write test, this leads to greater test coverage of the application.
When it comes to making a deployment to your users, having this large set of tests, which can be run before each deployment, there is more chance that any bugs that have crept into the application will be found before the application is deployed to the end-user.
Within your release process, you can have all the unit tests be run automatically. If any tests fail, the deployment of the application will be stopped. Then the team can look at what caused the test to fail, and fix this issue.
Having these issues caught before the application is deployed to the end-user, means that they will have confidence in using the application. You also as a business owner can have confidence that your application is being released to your paying customers, with the application being thoroughly tested.
The second great point that Erik made was Tighter Feedback Loop for Time Savings. In this section, Erik makes the point that having Unit Tests improves the feedback loop that developers use to see if errors are appearing in their code.
What is this Feedback Loop?
This feedback loop that Erik mentions is where the developer is given feedback straight away if there is a problem in their code, it’s not doing what it should be doing, the code is not fulfilling the requirements that have been set out in the user story.
For example, if you have an Angular based business application, that has the requirement that when the user clicks on the Login button, the application should open a login panel.
So the developer builds the Login section and adds a Login button that loads the Login section. As part of this, they need to check that the user is not already logged in. Now in their code, they could have a function which clears any current login sessions. This code could have a bug in it where it fails to clear all the logged in sessions. So being a good Angular developer, they write a Unit Test that checks for the list of login sessions, and confirms that this list is 0 when the Login button has been clicked (this confirms that when the user clicks Login, any previous logins have been cleared so they never see someone else account details).
Now 6 months later a new requirement has come in that the Login process needs to write to a database when the login was made so a report can be produced to show user logins. As part of adding this new functionality the clear logins code gets amended and a bug is introduced. It looks like its still working, but the login sessions aren’t being cleared.
Without a Unit Test to check that the functionality of the code still works as expected, this bug could get through to the paying customer, causing major problems.
With the developer using Unit Tests, they would get feedback straight away that the changes they are making to this Login process have caused this new bug. They will fix the issue even before it goes any further.
As Erik says, A unit test suite makes you much more likely to catch errors sooner than later. It does this by tightening the feedback loop. so with a good test suite in place, you’re far less likely to spend disproportionate amounts of time tracking down, reproducing, and fixing issues and the code you’ve built on top of them.
Reducing this time tracking, reproducing and fixing issues, saves money and gets the application out to the customer sooner than later.
Unit Tests are important to a project, especially a long-term business critical application. They have a real benefit to the business and are not something a developer is just ‘wasting’ time with.
The full article by Erik has some really good points and is well worth reading, whether you are a developer or a project manager of a business owner.