I understand what you're saying, but in my experience that's not very robust.
I've often found that an internal function might have a parameter that goes unused in any of the external tests, simply because it's too difficult to devise external tests that will cover every possible internal state or code path or race condition.
So the internal tests are used to ensure complete code coverage, while external tests are used to ensure all "main use cases" or "representative usage" work, and known frequent edge cases.
That doesn't mean the external tests aren't adding value -- they are. But sometimes it's just too difficult to set up an external test to guarantee that a deep-down race condition gets triggered in a certain way, but you can test that explicitly internally.
It's not that anyone is writing tests poorly, it's just that it simply isn't practically feasible to design external tests that cover every possible edge case of internal functionality, while internal tests can capture much of that.
And if your test suite takes 3 hours to run, there are many types of organizational solutions for that... but this is the first I've everd heard of "write less tests" being one of them.
I've often found that an internal function might have a parameter that goes unused in any of the external tests, simply because it's too difficult to devise external tests that will cover every possible internal state or code path or race condition.
So the internal tests are used to ensure complete code coverage, while external tests are used to ensure all "main use cases" or "representative usage" work, and known frequent edge cases.
That doesn't mean the external tests aren't adding value -- they are. But sometimes it's just too difficult to set up an external test to guarantee that a deep-down race condition gets triggered in a certain way, but you can test that explicitly internally.
It's not that anyone is writing tests poorly, it's just that it simply isn't practically feasible to design external tests that cover every possible edge case of internal functionality, while internal tests can capture much of that.
And if your test suite takes 3 hours to run, there are many types of organizational solutions for that... but this is the first I've everd heard of "write less tests" being one of them.