F# development and unit testing? [closed]

Question

I just got started with F#, which is my first functional language. I have been working quasi-exclusively with C#, and enjoy a lot how F# leads me to re-think how I write code. One aspect I find a bit disorienting is the change in the process of writing code. I have been using TDD for years in C# now, and really appreciate to have unit tests to know where I am at.

So far, my process with F# has been to write some functions, play with them with the interactive console until I am "reasonably" sure they work, and tweak & combine. This works well on small-scale problems like the Euler Project, but I can't imagine building something large that way.

How do people approach unit testing and building a test suite for a F# program? Is there an equivalent to TDD? Any pointers or thoughts are appreciated.

Answer 1

Test-driven developers should feel right at home in functional languages like F#: small functions that give deterministically repeatable results lend themselves perfectly to unit tests. There are also capabilities in the F# language that facilitate writing tests. Take, for example, Object Expressions. You can very easily write fakes for functions that take as their input an interface type.

If anything, F# is a first-class object-oriented language and you can use the same tools and tricks that you use when doing TDD in C#. There are also some testing tools written in or specifically for F#:

• NaturalSpec
• FsCheck
• FsTest
• FsUnit

Matthew Podwysocki wrote a great series on unit testing in functional languages. Uncle Bob also wrote a thought provoking article here.