Property Based Testing

FunctionalConf 2018

Property based testing course with hedgehog.

The Workshop

This workshop is an introduction to property based testing. The format of the workshop will be an interactive session with a mix of demonstration and practical exercises.

The material that we will work through is:

• Basics: Getting started writing understand and writing properties.
• Generators: Understanding how we generate data for our tests.
• Patterns: The repeating patterns of property tests.
• Practice: Getting better at finding and writing properties.
• Advanced: Advanced techniques that can be useful for testing more complex scenarios.

Please work through the following set-up instructions before the workshop. This will allow the workshop to commence on time.

Exercises will be exposed shortly before the workshop to ensure that everyone starts at the same point.

Getting Set-Up

There are three basic steps that should be done before the workshop:

1. Install haskell.
2. Clone this repository.
3. Do an initial build so the dependencies are available.

Installing Haskell

This workshop should work with any ghc/haskell 8.2, 8.4 or 8.6 you find easy to get set-up with. One option for doing this is following the instructions at https://www.haskell.org/platform/.

To verify your install, you should be able to run:

ghc --version

Clone this repository.

git clone https://github.com/markhibberd/property-based-testing-workshop.git

Initial Build

We will be using ghci directly for the workshop, so please set-up using cabal.

# Set-up using cabal install

cabal new-build --enable-tests

Running Tests

Load ghci:

cabal new-repl test

To run one test:

Hedgehog.check Test.Basics.prop_introduction

To run all the tests in a module.

Test.Basics.tests

To run all the tests.

Main.main

To sample the output of a generator:

Hedgehog.Gen.sample Test.SimpleGen.int

If these don't work for you, now is the time to ask for help, being able easily to run the tests is import as you work through the problems.