[Haskell-cafe] TDD in Haskell

[Christopher Done]

On 25 May 2010 13:36, Ionut G. Stan <ionut.g.stan at gmail.com> wrote:
> I'm doing TDD in pretty much all of the languages that I know, and I want to
> introduce it early in my Haskell learning process. I wonder though, if
> there's some established process regarding TDD, not unit testing.
>
> I've heard of QuickCheck and HUnit, but I've also read that QuickCheck is
> used mostly for testing pure code, while HUnit for impure code?
>
> What framework lends itself better for writing tests before the actual
> production code? Can you point out to some resources regarding this?

Real World Haskell has a chapter dedicated to writing Tests for your
code using QuickCheck[1]. The writers of this book work in industries
where well tested programs are essential.

Personally I suppose I follow a methodology of type driven development
followed by tests. I wrote a simple Emacs library to make testing
QuickCheck properties easier[2]. It's convenient because it lets you
check a function when your cursor is at the definition, or test all
properties in the current file. It picks up properties by symbols
named foo_prop, where foo is the function that the foo_prop property
is written for. Maybe this workflow suites your needs.

> Oh, and a small off-topic question? Is it considered a good practice to use
> implicit imports in Haskell? I'm trying to learn from existing packages, but
> all those "import all" statements drive me crazy.

I would follow tibbe's Haskell style guide[3] because it is strict and
reasonable. To quote it on this topic:

"Always use explicit import lists or qualified imports for standard
and third party libraries. This makes the code more robust against
changes in these libraries. Exception: The Prelude."

[1]: http://book.realworldhaskell.org/read/testing-and-quality-assurance.html
[2]: http://www.emacswiki.org/emacs-en/QuickCheckHaskell
[3]: http://github.com/tibbe/haskell-style-guide/blob/master/haskell-style.md