In my opinion, the project should be in a working state (everything builds, all tests pass, and the built binary or library would be usable) after every commit.

In my opinion, the project should be in a working state (everything builds, all tests pass, and the built binary or library would be usable) after every commit. Additionally, every commit should also contain unit tests for the code that's being changed, if possible. Sometimes it's possible to meet these criteria after writing just 30 lines of code, but more commonly it will take 100-300 lines of code and several hours to get to that state.