I like to treat tests as extended compiler warnings. E.g. in Haskell the type system is so strong, that once the compiler stops yelling at you, your code is more often than not correct. To catch the latter case, I like to write properties in QuickCheck.
QuickCheck is a Haskell framework. It allows you to formulate properties about your functions. Like --- given any list of comparable items, `sort' should conserve its length, produce an ordered list, and conserve the occurrence (and non-occurence) of each item. It should also be idempotent.
QuickCheck then generates a lot of random inputs and tests whether your properties hold. You (almost) never have to write test cases by hand. And since Haskell is pure, you never have to care about setting up the right state before invoking your tests.
This approach allows me to code with success, even when I am not intensively focused. (Of course Haskell helps with this even without QuickCheck. Not having to worry about state, assignment, order of execution, loop indices or recursion keeps the number of items I need to hold in my working memory low.)
Right. With Haskell and OCaml, a lot of testing can be pushed onto the type system. The language is better about letting you express semantic constraints via types, without making you declare every single instance of everything the way C and its descendants do.
I wrote a QuickCheck-eqsue library for Lua, FWIW: http://silentbicycle.com/projects/lunatest/ (It's the first released version, and the documentation still needs work...) For table "objects" and userdata, it checks the metatable for how to generate an arbitary instance.
> With Haskell and OCaml, a lot of testing can be pushed onto the type system.
Yes. There's even a paper about how to guarantee the balance invariants in a red-black tree with the type system. (Can't find it now, it's probably written by Ralf Hinze.) You can see an implementation at http://www.cs.kent.ac.uk/people/staff/smk/redblack/rb.html
QuickCheck is a Haskell framework. It allows you to formulate properties about your functions. Like --- given any list of comparable items, `sort' should conserve its length, produce an ordered list, and conserve the occurrence (and non-occurence) of each item. It should also be idempotent.
QuickCheck then generates a lot of random inputs and tests whether your properties hold. You (almost) never have to write test cases by hand. And since Haskell is pure, you never have to care about setting up the right state before invoking your tests.
This approach allows me to code with success, even when I am not intensively focused. (Of course Haskell helps with this even without QuickCheck. Not having to worry about state, assignment, order of execution, loop indices or recursion keeps the number of items I need to hold in my working memory low.)