Property-Based Testing with PropEr, Erlang, and Elixir

Thinking in Properties

Question 1

Your answer could be any three of these strategies:

• Modeling—comparing the implementation with a simpler but obviously correct one

• Generalizing traditional tests by automating steps we would do by hand
• Finding program invariants to validate
• Using symmetric properties

Question.

Question 2

Two example solutions:

Erlang         code/ThinkingInProperties/erlang/pbt/test/prop_solutions.erl

%% @doc this function tests that any lists of `{Key,Val}' pairs
%% end up being able to be sorted by the key by using `lists:keysort/2'.
prop_keysort1() ->
    ?FORALL(List, list({term(),term()}),
        begin
            %% is_key_ordered checks that all tuples' keys are ordered.
            is_key_ordered(lists:keysort(1, List))
        end).