PropCheck.Derive

Generating simple PropCheck generators from type definitions.

Usage

In order to derive a PropCheck generator with PropCheck.Derive, add a use statement to the module for which you want to derive the generators, or use an explicit module argument to define the module for which generators are to be generated. PropCheck.Derive will then attempt to create a generator for each @type. There are some requirements which must be fulfilled in order to do that:

Cyclic types are not allowed. PropCheck.Derive should detect those and raise an error.
Some types are not supported. For example, pid() cannot be created. Other types such as maybe_improper_list are not yet implemented, as their semantics are not clear.

Usage within a module

iex> use PropCheck
iex> Application.ensure_all_started(:propcheck_derive)
iex> defmodule Hello do
...> use PropCheck.Derive
...> @type my_type :: integer()
...> end
iex> {:ok, my_type} = produce(Hello.Generate.my_type())
iex> is_integer(my_type)
true

Usage outside of a module

iex> use PropCheck
iex> Application.ensure_all_started(:propcheck_derive)
iex> use PropCheck.Derive, module: String
iex> {:ok, string} = produce(String.Generate.t())
iex> is_binary(string)
true

License

PropCheck.Derive is licensed under GPL 3 as is PropCheck.

Quality of the generators

Please note that hand-written generators are likely to be better suited for non-trivial types. PropCheck.Derive makes use of oneof/1 and other simple union generators, but it does not use frequency/1 or similar generators to make some cases more likely then others.

TODOs

The semantics for maybe_improper_list is unclear. Can we add generators for that type?
Opaque types are not handled. Should we create a generator for them?