@threlte/test
is a lightweight component testing toolkit for Threlte.
npm i @threlte/test
It supports Svelte 4 + Threlte 7 and Svelte 5 + Threlte 8.
import { describe, it, expect } from 'vitest'
import { render } from '@threlte/test'
import Scene from './Scene.svelte'
describe('Scene', () => {
it('creates a box mesh with a boxGeometry and meshStandardMaterial', () => {
const { scene } = render(Scene)
const mesh = scene.getObjectByProperty('isMesh', true) as Mesh
expect(mesh).toBeDefined()
expect(mesh.material).toBeInstanceOf(MeshStandardMaterial)
expect(mesh.geometry).toBeInstanceOf(BoxGeometry)
})
})
It provides a function, render
, which will instantiate a Threlte context and whatever component you pass to it.
Calling render
will provide useful tools for testing your component's behavior.
const {
component, // SvelteComponent
scene, // THREE.Scene
camera, // CurrentWritable<THREE.Camera>
advance, // (delta?: number) => void
fireEvent, // (object3D: THREE.Object3D, event, payload) => Promise<void>
rerender, // (props) => Promise<void>
unmount, // () => void
} = render(Component)
scene
is the THREE.Scene
created by a Threlte context without any modifications. Querying objects from it can be useful for verifying that your component is doing what you expect it to.
In the test renderer environment, Threlte's render mode is set to manual
. If you wish to test results produced by running useTask
, you must call advance
. advance
is very similar to the function of the same name returned by the useThrelte
hook, but it advances at a fixed rate (16ms) regardless of environment. The number of times called and delta can also be configured when calling it.
// Runs advance() 10 times with a 33.3ms delta
advance({ delta: 33.3, count: 10 })
advance
will also return a flag indicating whether calling it resulted in a frame invalidation.
const { frameInvalidated } = advance()
If your component uses the interactivity
plugin, you can test events using the fireEvent
function. Let's say we have a component like this:
<script lang="ts">
export let onClick
</script>
<T.Mesh on:click={onClick}>...</T.Mesh>
We can write a test like this:
const onClick = vi.fn()
const { render, fireEvent } = render(Scene, { onClick })
const mesh = scene.getObjectByName('myMesh')
await fireEvent(mesh, 'click', someOptionalCustomPayload)
expect(onClick).toHaveBeenCalledOnce()
Note that if you use the event object, you will have to design a mock payload.
We recommend using @threlte/test
with Vitest as your test runner. To get started, add the threlteTesting
plugin to your Vite or Vitest config.
// vite.config.js
import { svelte } from '@sveltejs/vite-plugin-svelte'
import { threlteTesting } from '@threlte/test/vite'
export default defineConfig({
plugins: [
svelte(),
threlteTesting(),
]
});
Additionally, the Vitest environment must be set to a DOM enviroment.
The test renderer runs in a node.js environment, and it does not attempt to mock a webgl canvas, which can become quite complicated. Instead, it creates a Threlte context and renders your component as a child of a Threlte <SceneGraphObject>
. This means that testing <Canvas>
or WebGLRenderer
related configuration and behavior won't work.
This libary's primary purpose, however, is to allow you to test whether your component works in isolation as you intend it to work.