Gain insights into property-based testing with PropEr in Erlang. Delve into foundational principles, common frameworks, custom data generators, and applying testing in realistic projects for robust code validation.

Property Based Testing with PropEr in Erlang_468 x 60 copy.png

propert-based-testing.tar.gz

Erlang

Elixer

Erlang-Chap2

Elixir-Chap2

Erlang-Shell

erlang-user

elixir-user

elixir-shell

elrang-eunit

erlang-chap5-employee

elixir-cover_test

erlang-cover_test

erlang-chap10-databaseinit

erlang-chap10-user

elixir-chap10-user

erlang-chap10-shell

elixir-chap10-shell

erlang-chap10-dbsetup

elixir-chap10-dbSetup

erlang-chap5-templating

erlang-chap5-last

elixir-chap5-last

erlang-chap10-default

elixir-chap10-default

elixir-chap10-default-copy

Erlang-Chap2-copy

Elixir-Chap2-copy

Erlang-Shell-copy

elixir-shell-copy

erlang-default-force

elixir-default-force

erlang-test-shell

elxir-test-shell

Property-based testing relies on specifying some property of code, rather than unit tests which specify the expected output in response to some inputs. In this course, you’ll cover the concepts you need to get started, up to the point where you feel confident enough to use the most advanced features of PropEr with Erlang.

You’ll start smoothly with the basic and foundational principles of property-based testing. From there, you will cover some of the common frameworks, how to think in properties, how to write your own custom data generators, and more. You'll also see how you can use Property-Based Testing in a realistic project.

By the time you finish this course, you will be comfortable testing real-world applications using properties.

Property-Based Testing with PropEr in Erlang

# The implementation

A simple method is to count how many of each item is in the list. Account for the specials first, reducing the count every time the specials apply, and then run over the list of items that are not on sale.

```erlang
-type item() :: string().
-type price() :: integer().
-type special() :: {item(), pos_integer(), price()}.

-spec total([item()], [{item(), price()}], [special()]) -> price(). 
total(ItemList, PriceList, Specials) ->
    Counts = count_seen(ItemList),
    {CountsLeft, Prices} = apply_specials(Counts, Specials), 
    Prices + apply_regular(CountsLeft, PriceList).
```

Here, `count_seen/1` should create a list of each item and how many times it's been seen. We then pass that data to `apply_specials/2`, which returns a tuple with two elements: the number of items not processed as part of a special on the left, and the summed-up prices of all specials on the right. Finally, we take that sum, and add it to the cost of the rest of the items, as defined by `apply_regular/2`.

This method is almost the opposite of how we approach the test. Rather than generating both lists and mashing them together, this splits them up to get the final count.

# Helper functions

Here we have the `count_seen/2`, `apply_specials/2`, and the `apply_regular/2` functions that will allow us to generate the total price.

Take a look at the implementation of the specials module. 

Implementing Specials

Take a look at the implementation of the specials module.

Foundations of Property-Based Testing

Writing Properties

Thinking in Properties

Custom Generators

Responsible Testing

Properties-Driven Development

Shrinking

Targeted Properties

Stateful Properties

Case Study: Bookstore

State Machine Properties

Conclusion

Implementing Specials

The implementation