Understanding Different Types of Testing

The testing spectrum spans from end-to-end testing (by manipulating the user interface) to integration tests, and finally to unit tests. End-to-end tests test everything, including the user interface, the underlying HTTP services, and even database interactions; nothing is mocked. For example, if you've got an e-commerce application, an end-to-end test might actually place a real order with a real credit card, or it might place a test order, with a test credit card.

End-to-end tests are costly to run and maintain. They require the use of full-blown browsers controlled through programmatic drivers such as Selenium, WebdriverIO, or Cypress. This type of test platform is costly to run, and small changes in the application code can cause end-to-end tests to start failing.

Integration or system-level tests ensure that a set of systems is working as expected. This will usually involve deciding on a limit as to where the system under test...