InfoQ: Full Stack Testing: Balancing Unit and End-to-End Tests

Full Stack Testing: Balancing Unit and End-to-End Tests: 

"At their core, tests make sure your application is doing what you intend it to do. They are an automated script to execute your code and check that it did what you expected. The better they are, the more you can rely on them to gate your deployments. Where your tests are weak, you either need a QA team or you ship buggy software (both mean your users get value at a much slower pace than is ideal). Where your tests are strong, you can ship confidently and quickly, without approvals or slow, manual processes like QA. You must also balance the future maintainability of the tests you write. 



Your application will change and thus so will your tests. Ideally, your tests only have to change proportionally to the change you are making in your software. If you are making a change in an error message, you don’t want to have to rewrite a lot of your test suite. But, if you are completely changing a user flow, it reasonable to expect to rewrite a lot of tests. 



Practically speaking, this means you can’t do all your testing as end-to-end full-blown integration tests, but you also can’t do it as nothing but tiny little unit tests. This is about how to strike that balance."




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