Why automated testing is essential in software development

Automated testing is an essential part of modern software development. High-quality software is easier to work with, has fewer issues, and continues to function properly when new features are added. Quality doesn’t happen by chance; rigorous testing is the final and crucial step before deployment. In this article, you’ll learn how testable systems are built, the differences between manual and automated testing, and how to create testable systems.

Testable systems are the result of understandable, highly cohesive, and “loosely coupled” code. The latter means that a change in one part of the system does not directly cause another change or issue. “Highly cohesive” refers to systems where similar task areas are clustered together. Systems built in this way are easier to understand, making the software quicker to comprehend and easier to expand, adjust, or debug.

Benefits of automated testing

Software testing is increasingly being automated, and there are many reasons for this. As systems grow larger, manual testing requires more human effort. It takes a relatively long time, which means software releases happen less frequently. Moreover, since manual testing is routine, recurring errors may slip through. With automated testing, the expected behavior of functionality is encoded so that a computer can perform the test. Developers automatically receive reports detailing any identified errors.

Although automated testing does require an additional coding step, its benefits are substantial. Encoding specifications is a one-time process – unless you want to test new functionality. Coding specifications forces testers and developers to think about what the functionality should do. Automated testing can be performed in a short time and the process can be repeated flawlessly.

Test-Driven Development (TDD)

In software development, you can already account for automated testing in advance. With Test-Driven Development (TDD), developers write automated unit tests before they write the code. This forces developers to think ahead about the steps needed to implement a function. It also leads to less complex systems, as testers strive for simplicity in this approach. Developers who apply TDD are generally faster and deliver systems with fewer defects than those who work with conventional methods.

Three types of automated testing

There are three main types of automated testing: unit testing, acceptance testing, and end-to-end testing.

• Unit Testing: This is performed by developers to validate the functionality of units – the smallest components of the code. In most object-oriented languages, these are “classes,” but they can also be “methods” or “functions.” Unit tests, however, do not evaluate the composition of the units. To validate that everything works as intended, acceptance tests are needed.
  
• Acceptance Testing (also called integration or system testing): These are formal documents specifying how a system should behave from a business perspective. While unit tests are written by and for developers, acceptance tests are written by and for the end users. Unit tests focus on internal quality, while acceptance tests assess external quality. When writing acceptance tests, Behavior-Driven Development (BDD) frameworks are often used, such as SpecFlow for C#, Cucumber or Fitnesse for Java, Codeception for PHP, or Ginkgo/GoBDD for Go.
  
• End-to-End Testing: This type of testing interacts with the system via the user interface by sending messages to an API, calling web services, and analyzing reports. The process of end-to-end testing is slower than unit testing, but it is highly valuable. End-to-end tests ensure that all integrated components of a system (from the front-end and back-end to databases and external APIs) work together as expected.

Automated testing in CI/CD software development

In software developed based on Continuous Integration/Continuous Delivery (CI/CD) principles, all tests are automated before any changes are deployed to production. This is easiest with development platforms such as Azure DevOps and GitLab, which natively support the execution of unit tests. End-to-end acceptance tests, however, need to be performed in a real environment. If such an acceptance test fails, the failure status in the CI/CD pipeline ensures that the software is not deployed to production.

Best practices for automated testing

Finally, here are four best practices for automated testing during software development:

1. Keep test suites as small as possible. Focus on what the system should do, not what it shouldn’t do. This means testing the expected flow, not all possible error scenarios.
2. Focus on critical paths. The greater the impact when something goes wrong, the more important it is to test it automatically.
3. Like code, tests also require regular refactoring. Clean tests are just as important as clean code. Schedule regular time to clean up your tests.
4. Tests should not depend on the presentation of the GUI (graphical user interface). GUIs are changeable, so GUI tests should be based on elements within the interface, not on aspects such as position or color.

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