The FicusJS testing package provides lightweight helper functions for web component testing.

This package provides browser globals such as window and document using jsdom which is an implementation of many browser APIs ideal for testing but is not an actual browser.

We recommend using a tool such as Cypress for browser end-to-end tests.

Running tests

This package contains functions intended for a NodeJS environment and not a real browser. It is therefore, best used for fast iteration.

The functions can be used with any NodeJS testing framework.

The following functions are available in the FicusJS testing package.

  • init - a function for initializing the test environment
  • render - a function to render a web component for testing

init function

The init function initializes the NodeJS environment ready for testing.

Simply call init in your set-up hook.

import test from 'ava'
import { init, render } from '@ficusjs/testing'


// if passing options to JSDOM
test.before(() => init({ runScripts: 'dangerously' }))

The init function accepts the following optional arguments:

optionsobjectAn object of options to pass to JSDOM

render function

The render function will create a new web component instance for testing.

It returns a DOM instance of the component.

import test from 'ava'
import { init, render } from '@ficusjs/testing'


test('render basic component', async t => {
const comp = await render('basic-comp', () => import('../src/component.mjs'))
t.is(comp.querySelector('p').textContent, 'Basic component')

The render function accepts the following arguments:

tagNamestringThe web component tag name
importerfunctionA function that registers a web component. This can return a Promise

Testing components

Testing web components can be done in a number of ways.

  • verifying that a component renders without throwing using a "smoke test"
  • shallow rendering and testing component output
  • full rendering and testing component lifecycle and state changes

It is a good idea to start with creating basic smoke tests for your components.

Testing that a component mounts and ensures that it doesn't throw during rendering provides a lot of value with very little effort.