There are standard best practices that recommend writing automated tests. However, not all developers use them in real projects. Let us see how automated tests can be beneficial in obvious and not obvious ways for any project.

Stability

The primary purpose of all automation tests is to make sure that the application works as expected. Expectations may include code level checks, functional requirements, visual representation, performance limitations, proper security, etc.

Each of the expectations mentioned above guarantees stability in one or several areas critical to the customers. If nobody performs such checks, then the application may crash without any warning, and customers are not going to be happy about that.

To prevent this issue application has to have automated tests and an environment (e.g., Continuous Integration server) to run them regularly. It is crucial to maintain state when all tests passed to guarantee proper work of the application. If some tests have failed, then the application has to be considered broken. It should maintain this status up to the moment when all tests are fixes and passed again.

Time

There is a typical delusion that writing tests is not worth it and only takes time. It is not valid for most of the projects because the project cycle includes not only the initial development but also upgrades and maintenance. Tests may indeed take some time to implement during the initial development phase, usually up to 30% of development time. However, they are going to save time during each following phase as tests may substitute 90% of manual testing and so save much time for QA engineers.

Another common mistake is writing too many tests. Some projects may indeed need 100% coverage in every area (code, functionality, UI, etc.) to guarantee that is works properly, but most projects can use a simplified approach. This approach assumes that each higher test level thinks that the lower test level covers all the use cases, and it has to test only the integration scenarios without retesting all scenarios from the lower level. It is widely known as the test pyramid.

Maintenance

Properly written tests are great tools that every developer can use to understand how each feature works. Usually, tests contain input data and expected results, and so a developer may use this data to understand internal logic and the way feature works.

Good test coverage also simplifies upgrades and releases a lot. Developers and QA engineers do not need to spend extra time on manual testing. Instead, tests immediately show which parts do not work after the upgrade, or what features do not function as expected in the future release.

If the application has enough tests, and they are running regularly, then developers may immediately identify and fix all found bugs and issues. So, tests improve code quality, decrease the number of issues, and maintain functional requirements all over the application. These are the most important consequences of good code coverage, and every application has to utilize them to satisfy its customers.