Property-Based Testing with PropEr, Erlang, and Elixir

Writing Properties

Question 1

proper_gen:pick(proper_type:Type())

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Question 2

What the property is doing is validating the lists:seq(Start, Stop) function, which would be expected to return a list of integers in the range [Start, ..., Stop]. For example, running lists:seq(2,5) should return [2,3,4,5]. The property does the validation of this by looking at two aspects of such a list:

• The list should contain as many entries as the range covered by both terms (2..5 has 4 entries, or just (5-2)+1).

• To avoid having the test succeed on outputs such as [1,1,1,1], the increments/1 function is used to ensure that each number is greater than the next one.

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