I find the easiest way (for me) to identify what type of test is running is by looking at responsibility. - A unit test is single responsibility. It tests jus

I find the easiest way (for me) to identify what type of test is running is by looking at responsibility. - A unit test is single responsibility. It tests just that one bit of code with all dependencies stubbed, abstracted, mocked, or removed from consideration in some way. - An integration test is multiple responsibility. It tests just one bit of functionality as a vertical slice through the stack (including [only] relevant dependencies) with all other aspects of the code base eliminated from consideration. - An end to end test is full responsibility. It tests a complete path through all the functionality necessary to complete a 'journey' as a user/consumer of the app/tool. So for example VAT calculation is unit tested as isolated code, invoicing is integration tested as a vertical slice including database etc, and order processing is end-to-end tested from placing the order through to its completion. That's a simplified example and not always accurate depending upon the system and the team perspectives/opinions, but the principle of looking at responsibilities is a very useful rule of thumb.