This this this!

Most often I see TDD used as a couch for a really bad type system.

Types are just formalised limited contracts. Emphasis on limited. They are not enough.

T(est)DD does tend to make your code look more like you used a functional-oriented language. A lot less mutability, heavier use of first-class functions, etc. Though I tend to prefer languages that are at least somewhat functional (eg. python, go).

> Though I tend to prefer languages that are at least somewhat functional (eg. python, go).

Can't think of any less functional languages than these.

Think of the language features you need to be able to program in a functional way, then think about what these languages have. There is a sizable overlap.

If you need a template then think of scheme. It is the best example of a minimal functional language.

It doesn't even help people enough apply SOLID principles.

Pure functions help but the principles of generalisation are deeper than this.

Tests verify contracts offline. This will miss real issues.