While REPL-driven development isn't a widely recognized term, it is my favored style of development and has a particular bearing on testing. This style of development is very common when working with interpreted languages, such as Lisp, Python, Ruby, and JavaScript.
When you work with a Read-Eval-Print-Loop (REPL), you write small functions that are independent and also not dependent on a global state.
The functions are tested even as you write them.
This style of development differs a bit from TDD. The focus is on writing small functions with no or very few side effects. This makes the code easy to comprehend, rather than when writing test cases before functioning code is written, as in TDD.
You can combine this style of development with unit testing. Since you can use REPL-driven development to develop your tests as well, this combination is a very...