add a function in cy test code example

Example: cypress custom command with this

Cypress.Commands.add('login', (userType, options = {}) => {
  // this is an example of skipping your UI and logging in programmatically

  // setup some basic types
  // and user properties
  const types = {
    admin: {
      name: 'Jane Lane',
      admin: true,
    },
    user: {
      name: 'Jim Bob',
      admin: false,
    }
  }

  // grab the user
  const user = types[userType]

  // create the user first in the DB
  cy.request({
    url: '/seed/users', // assuming you've exposed a seeds route
    method: 'POST',
    body: user,
  })
  .its('body')
  .then((body) => {
    // assuming the server sends back the user details
    // including a randomly generated password
    //
    // we can now login as this newly created user
    cy.request({
      url: '/login',
      method: 'POST',
      body: {
        email: body.email,
        password: body.password,
      }
    })
  })
})