Testing Pyramid
Khaled El-Morabea, Hassaan El-Garem · Apress eBooks · 2021
Now that we know how to use XCTest and XCUITest to write tests in iOS, we need to know the types of tests we should be writing, as well as the quantity of each type of testing. And this is where the “Testing Pyramid" comes in. It is a concept that helps in answering both of these questions. Mike Cohn came up with this concept in his book Succeeding with Agile. It's a great visual metaphor telling you to think about different layers of testing. It also tells you how much testing to do on each layer.