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

This chapter has shown us the basics of stateful property testing, based on a single simple model. We’ve been through the two phases of the testing: 
1. Symbolic testing, where the model is used to generate a sequence of commands that represents what the system should do.
2. Real testing, where the symbolic sequence of commands is applied to the real system, and the results are compared with what the model expects.

We’ve put these concepts in practice through a cache server modeled as a first-in-first-out list and showed that the model seems to hold fine under sequential operations. We’ve then seen how PropEr can take that same exact model and create a parallel version of it that could, with some amount of help, find concurrency bugs in our cache program.

# What's next

We’ve seen the base mechanism of how stateful properties work, but truth be told, the cache example we used resulted in a rather simple model. In the next chapter, we’ll experiment with a more complex stateful system based on SQL queries, with varying amounts of determinism. We’ll move past the basics of stateful properties and explore more advanced techniques to handle the complexity of modeling large systems for integration tests.

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