happy.js

import { render, fireEvent } from '@testing-library/react'

test('should submit a valid form', () => {
  const { getByLabelText, getByText } = render(<App />)
  const setValue = value => ({ target: { value } })
  const password = '123456'
  const email = 'foo@bar.com'

  fireEvent.input(getByLabelText('Email'), setValue(email))
  fireEvent.input(getByLabelText('Password'), setValue(password))
  fireEvent.input(getByLabelText('Confirm your password'), setValue(password))
  fireEvent.click(getByText('Submit'))

  expect(axios.post).toHaveBeenCalledWith('http://localhost:5000', {
    email,
    password
  })
})