There is an argument that a static type system is a set of built in unit tests, that you can activate by adding a command word in a particular position. And th

There is an argument that a static type system is a set of built in unit tests, that you can activate by adding a command word in a particular position. And that the test harness on code in a dynamic languages is a domain specific compiler. The problems come when you want to turn off specific type tests for a particular bit of code because it is deliberately bending the rules (I see this a lot in Go), or the domain specific compiler you've built isn't comprehensive in its coverage not just of lines of code, but the structural complexity of the code.