Fiz o teste usando a class e deu certo!!!
/// <reference types="Cypress" />
describe('alura,pic.js', () => {
beforeEach(() =>{
cy.visit('https://alura-fotos.herokuapp.com/')
})
it('verifica letra maiuscula no usuário', () => {
cy.contains('a', 'Register now').click()
cy.get('input[formcontrolname="userName"]').type('ADRIANA')
cy.contains('.btn', 'Register').click()
cy.contains('.text-danger', 'Must be lower case').should('be.visible')
})
})
