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.

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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

# Summary
In this chapter, we’ve been through a realistic integration test suite written as stateful properties. We began with a model layer with no tests for a bookstore using a PostgreSQL instance. We first started by drawing up the generators for our base data types, which helps do some broader testing to make sure the system works without throwing exceptions. That’s where we encountered and resolved our first encoding bug.

With this out of the way, we established the initial model, using a wrapper module (a shim) to allow as much determinism as possible. As we’ve seen, this approach tends to create a bit more repetition with precondition-heavy code, but makes tests more decidable and simpler to debug. We've also seen this at work as we refined the model through multiple failures and discovered more tricky aspects of using SQL.

Additionally, we’ve been through a round of debugging, and we’ve  seen how PropEr shrinks stateful property command sequences to debug our models before doing a final check with parallel tests.

# What's next
With this, we've seen most of what there is to see with stateful properties. The one exception is a specialization for systems that represent finite state machines, which we'll get to next.

Here's a summary of what we learned in this chapter.

Wrapping Up

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

Wrapping Up

Summary