next.js/test/unit/getDisplayName.test.js

/* eslint-env jest */
import { Component } from 'react'
import { getDisplayName } from 'next-server/dist/lib/utils'

describe('getDisplayName', () => {
  it('gets the proper display name of a component', () => {
    class ComponentOne extends Component {
      render () {
        return null
      }
    }

    class ComponentTwo extends Component {
      static displayName = 'CustomDisplayName'
      render () {
        return null
      }
    }

    function FunctionalComponent () {
      return null
    }

    expect(getDisplayName(ComponentOne)).toBe('ComponentOne')
    expect(getDisplayName(ComponentTwo)).toBe('CustomDisplayName')
    expect(getDisplayName(FunctionalComponent)).toBe('FunctionalComponent')
    expect(getDisplayName(() => null)).toBe('Unknown')
    expect(getDisplayName('div')).toBe('div')
  })
})