You can write far fewer tests if you have good static validation. For example, taken to the extreme, you can write 0 tests in Agda, and still have more assuran

You can write far fewer tests if you have good static validation. For example, taken to the extreme, you can write 0 tests in Agda, and still have more assurances about correctness than if you had 100% coverage in a dynamically typed program.