Expect

The @japa/expect plugin is a wrapper on top of jest-expect. Please read the Jest documentation to view the methods available on the expect object.

Suppose you have not configured the plugin during the initial setup. Then, you can install it from the npm registry as follows.

npm i -D @japa/expect@2.0.2

And register it as a plugin within the bin/test.js file.

import { expect } from '@japa/expect'
import { configure, processCliArgs } from '@japa/runner'

configure({
  ...processCliArgs(process.argv.slice(2)),
  ...{
    files: ['tests/**/*.spec.js'],
    plugins: [expect()]
  }
})

const { expect } = require('@japa/expect')
const { configure, processCliArgs } = require('@japa/runner')

configure({
  ...processCliArgs(process.argv.slice(2)),
  ...{
    files: ['tests/**/*.spec.js'],
    plugins: [expect()]
  }
})

Once done. You can access the expect property from the Test context as follows.

test('add two numbers', ({ expect }) => {
  expect(2 + 2).toEqual(4)
})

In Jest, the expect property is available globally. However, with Japa, we recommend you always read it from the Test context.