End-to-end testing is a type of software testing that automatically checks the entire flow of application from the user`s side. E2E testing identifies the performance of all system dependencies and components as well as its interaction with external systems in a real-life scenario.
To skip the theory you can find on the Internet, we want to provide you with the real-life example that proves a power of E2E testing.
We've used the external payment system in one of the online marketplaces. During E2E testing, the system has identified changes in the payments system APIs. The case was that the system started to require validation of data, that wasn't compulsory before. Such testing helped us to detect bugs, caused by the сhange in external services and significantly save developers` time.