Testing
Testing is equally important as writing the code. It is a way to ensure that the code is working as expected and to catch any bugs that may have been introduced before going to a live environment and affect the final user. It can be either manual or automated. Manual tests are usually done by people vs automated tests are done by machines.
No matter if you are in a small team or in a big company, testing is a must. We are human after all, and mistakes can happens.
There are different types of tests, where each layer described is important to cover because each has its own purpose. The most common types of tests are:
Unit test
Cover the smallest piece of code, usually a function or a method. The goal is to test the code in isolation, without any dependencies. Making sure any changes in the code will not break the expected behavior.
Test should be fast and deterministic (same result over and over). It should not depend on any external resource, such as a database, network, or file system.
Coverage
Coverage is a metric that measures the amount of code that is covered by tests. It generates a report showing which are the total lines of code, which are covered by tests and which are not.
The higher the coverage, the better. But it is important to note that 100% coverage does not mean that the code is bug free. It only means that all lines are covered by tests.
It is a good idea to check the coverage on your tests. If any line is not covered, means that test may not be completed or that the code is not being used, given you the opportunity to remove it.
Mocking
When testing logic that depends on external resources, such as a database or a external HTTP request, it is a good practice to mock the response. This way, the test is not dependent on the external resource, giving faster and deterministic tests.
Fixtures
Fixtures are a way to set up and tear down resources that are used in the tests. It is a way to avoid code repetition and to keep the tests clean, ensuring that data is consistent across all tests.
Parametrized tests
Parametrized tests are a way to run the same test with different inputs.
Integration test
Integration tests are used to test the interaction between different parts of the application. It is a way to ensure that the different parts are working together as expected.
End-to-end test
Tests the whole application against a live production-like server. It is a way to ensure that the application is working as expected from the user's perspective. Usually, it is done with a browser automation tool, such as Selenium. In case of an API, you can automate with Postman. If is not possible to automate, it can be done manually.
These tests are slow and hard to create and maintain, but are important to ensure that the application is working as expected.
Smoke test
Smoke tests are a subset of end-to-end tests. They are used to ensure that the the most important features of the application are working as expected, preventing the application to be usable. Smoked tests have a limited scope, completed in a short time.
Regression test
Confirms that previously developed and tested features in an application still works correctly after any changes are introduced. Regression tests have wider scope and covers all areas in the application, taking longer to complete.
Performance test
Performance tests are testing methods to measure how the system behaves and performs under a particular load.
Load test
Load testing is the process of checking the behavior of the system under an anticipated load.
Stress test
The goal of stress testing is to identify the saturation point and the first bottleneck of the application under test. Once is identified, it is possible to patch that part of the system to avoid the bottleneck.
Spike Tests
Test the system's reaction to sudden and extreme changes in load.