render.test.js

import { render } from '@testing-library/svelte'
import { VERSION as SVELTE_VERSION } from 'svelte/compiler'
import { describe, expect, test } from 'vitest'

import Comp from './fixtures/Comp.svelte'

describe('render', () => {
  const props = { name: 'World' }

  test('renders component into the document', () => {
    const { getByText } = render(Comp, { props })

    expect(getByText('Hello World!')).toBeInTheDocument()
  })

  test('accepts props directly', () => {
    const { getByText } = render(Comp, props)
    expect(getByText('Hello World!')).toBeInTheDocument()
  })

  test('throws error when mixing svelte component options and props', () => {
    expect(() => {
      render(Comp, { props, name: 'World' })
    }).toThrow(/Unknown options/)
  })

  test('throws error when mixing target option and props', () => {
    expect(() => {
      render(Comp, { target: document.createElement('div'), name: 'World' })
    }).toThrow(/Unknown options/)
  })

  test('should return a container object wrapping the DOM of the rendered component', () => {
    const { container, getByTestId } = render(Comp, props)
    const firstElement = getByTestId('test')

    expect(container.firstChild).toBe(firstElement)
  })

  test('should return a baseElement object, which holds the container', () => {
    const { baseElement, container } = render(Comp, props)

    expect(baseElement).toBe(document.body)
    expect(baseElement.firstChild).toBe(container)
  })

  test('if target is provided, use it as container and baseElement', () => {
    const target = document.createElement('div')
    const { baseElement, container } = render(Comp, { props, target })

    expect(container).toBe(target)
    expect(baseElement).toBe(target)
  })

  test('allow baseElement to be specified', () => {
    const customBaseElement = document.createElement('div')

    const { baseElement, container } = render(
      Comp,
      { props },
      { baseElement: customBaseElement }
    )

    expect(baseElement).toBe(customBaseElement)
    expect(baseElement.firstChild).toBe(container)
  })

  test.runIf(SVELTE_VERSION < '5')(
    'should accept anchor option in Svelte v4',
    () => {
      const baseElement = document.body
      const target = document.createElement('section')
      const anchor = document.createElement('div')
      baseElement.appendChild(target)
      target.appendChild(anchor)

      const { getByTestId } = render(
        Comp,
        { props, target, anchor },
        { baseElement }
      )
      const firstElement = getByTestId('test')

      expect(target.firstChild).toBe(firstElement)
      expect(target.lastChild).toBe(anchor)
    }
  )
})