I had that mindset for a while, just to fall into enough issues that I had to balance it again. Integration tests are important for features, unit tests stay i

I had that mindset for a while, just to fall into enough issues that I had to balance it again. Integration tests are important for features, unit tests stay important for code blocks. My realization was that a ton of what we wrote aren't features, but blocks. For instance, let's imagine an API that build an invoice. Where do you put the VAT calculation test ? Do you jam your 100+ VAT test cases in the integrations tests, or do you unit test the VAT calculation in isolation and only cover the main cases in the integration ones ? Same for name display, invoice number generation, Invoice items fetching etc. If you want a decent coverage and also document/properly test the edge cases, unit test will easily be half or more of your whole test volume. And of course you'll want to reuse there blocks, so make sure they're rock solid, so pay even more attention to tests.