[dpark]

Customers don’t care about your testing at all. They care that the product works.

Like most things, the reality is that you need a balance. Integration tests are great for validating complex system interdependencies. They are terrible for testing code paths exhaustively. You need both integration and unit testing to properly evaluate the product. You also need monitoring, because your testing environment will never 100% match what your customers see. (If it does, you’re system is probably trivial, and you don’t need those integration tests anyway.)

[axelriet]

Integration tests (I think we call them scenario tests in our circles) also only tend to test the happy paths. There is no guarantees that your edge cases and anything unusual such an errors from other tiers are covered. In fact the scenario tests may just be testing mostly the same things as the unit tests but from a different angle. The only way to be sure everything is covered is through fault injection, and/or single-stepping but it’s a lost art. Relying only on automated tests gives a false sense of security.