Property-Based Testing with PropEr, Erlang, and Elixir

Testing Specials

Alright, before moving further, let’s reevaluate our TODO list:

• Items are identified by unique names (nonempty strings).

• The list of items has no set length (though it appears nonempty), and the items it contains are in no specific order.

• The unit prices appear to be integers. (Not a bad idea, since floating point numbers lose precision; we can assume values are written in cents, for example.)

• The special prices are triggered only once the right number of items of the proper type can match a given special.

• All items have a unit price.

• It is not mandatory for a given item to have a special price.

That’s decent coverage in terms of features and requirements we extracted, with few lines of tests! It may not feel like we’ve accomplished ...