Quickstart

Set up

Create a new project

There is no need for a special project structure to introduce kiri-check. Simply create a regular project using the dart command (or flutter command).

dart create kiri_check_quickstart

Install

Install the library from pub.dev using the following command:

With Dart:

dart pub add dev:kiri_check

With Flutter:

flutter pub add dev:kiri_check

Alternatively, add the library to your pubspec.yaml and run dart pub get or flutter pub get.

dev_dependencies:
  kiri_check: ^1.2.0

Write a simple property

Writing a property is straightforward. kiri-check is integrated with package:test and can be used alongside it. There is no need to change existing unit test code; you can simply add properties.

Let’s write a very simple property. Create a file named simple_test.dart in the test directory and add the following code:

simple_test.dart:

property('generate integer', () {
  forAll(integer(), (value) {
    expect(value, isA<int>());
  });
});

This property uses the integer arbitrary to generate a random integer and verifies that the integer is of type int. This property will always succeed (provided there are no bugs in kiri-check).

Properties are defined with the property function. property accepts the same arguments as the test function from package:test. The forAll function used within the block passed to property takes an arbitrary that generates random values and a block that receives these values. In that block, you can verify the values using the expect function from unit tests.

Run the test

Running the test is the same as with package:test. Execute it with the dart test command.

dart test

If a property fails, shrinking will occur to display the smallest value that causes the error.

Where to next?

Whether you are familiar with property-based testing or not, it's a good idea to look through the list of arbitraries to get to know the main ones. If you're new to property-based testing, reading a book on the subject is also a good idea. Though it's intended for Erlang and Elixir, I recommend Property-Based Testing with PropEr, Erlang, and Elixir: Find Bugs Before Your Users Do (Japanese translation).