Writing Tests

Writing tests for your Joystick app starts and ends with the @joystick.js/test package (installed for you when running joystick create <app_name>), and more specifically, the test.that() method on the default export from that package.

Behind the scenes, Joystick relies on the Ava test runner. The @joystick.js/test package adds some helpful utilities around that library designed specifically for testing a Joystick app.

To showcase an example of writing a test, assume we have a generic function in our /lib folder called add() that adds two numbers together:

const add = (n1 = 0, n2 = 0) => {
  return n1 + n2;
};

export default add;

To write a test for this function, we'd create a file in our /tests directory at /tests/lib/add.test.js:

import test from '@joystick.js/test';

test.that('add function adds two numbers together', async (assert = {}) => {
  const add = await test.load('lib/add.js', { default: true });
  assert.is(add(5, 5), 10);
});

Above, we import the test default export from @joystick.js/test. That export is an object containing various methods for writing your tests.

Here, we use the test.that() function to write an individual test. test.that() takes a string describing the test being performed as the first argument and a callback function to perform the test. That callback function receives an object assert which contains various assertion methods for verifying the result of our test.

Inside of the test function, we utilize the test.load() method from @joystick.js/test which helps us to dynamically import code from our app. We give it a path relative to the root of our project as the first argument and as the second, an options object with default set to true, telling .load() to hand us the default export from the file at that path.

What we expect to get in return is the add() function we defined in that file. To test it, we call to assert.is() passing a call to the function add(5, 5) to add two numbers together. As the second argument to assert.is() we pass the expected result 10.

When we run this test in our cli with joystick test, we'd expect to get back a passing test. If we were to modify the above example to the following, we'd expect to get back a failing test:

import test from '@joystick.js/test';

test.that('add function adds two numbers together', (assert = {}) => {
  const add = await test.load('lib/add.js', { default: true });
  assert.is(add(5, 3), 10);
});

This is the core of writing a test for a Joystick app. While there are several other helper methods for testing specific functionality, this is all you need to know to get your hands dirty.

API Reference

test.that()

Function API

test.that(test_description: string, callback) => void;

Arguments