testing-using-jsdom.js

    ReactDom.render(e(CalculatorApp), document.getElementById('container'))

    const displayElement = document.querySelector('.display')

    expect(displayElement.textContent).to.equal('0')

    const digit4Element = document.querySelector('.digit-4')
    const digit2Element = document.querySelector('.digit-2')
    const operatorMultiply = document.querySelector('.operator-multiply')
    const operatorEquals = document.querySelector('.operator-equals')

    digit4Element.click()
    digit2Element.click()
    operatorMultiply.click()
    digit2Element.click()
    operatorEquals.click()

    expect(displayElement.textContent).to.equal('84')