cypress_salesforce_ui_login.js

const { SF_username, SF_password, SF_login_url } = Cypress.env()
describe('Programmatically log in to SF app', () => {
    
  it('makes XHR req & loads dashboard', () => {
          Cypress.log({name: 'loginViaOAuth'});

          cy.request({
            method: 'POST',
            url: SF_login_url,
            body: {
              un: SF_username,
              pw: SF_password,
            },
            headers: {
              'Content-Type': 'application/x-www-form-urlencoded',
              'user-agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:89.0) Gecko/20100101 Firefox/89.0'

            }
          }).then((resp) => {
              /* we then make this GET req for reference, so parse out what we need-
              https://mindful-koala-78jg04-dev-ed.my.salesforce.com/secur/frontdoor.jsp?sid=00D5e000004gjXb%21AQ4AQKUVRjtYzF4KZ3TxMZHKzwUAhccCRLqiyy_ASet8kvcGvpYLwpnIBqxJkO95cjZ8gSXGKy4GPO3Ndp0GSX7LHAzfbgTU&apv=1&allp=1&cshc=e000006atmje000004gjXb&display=page */
                          
              const locationParam = resp.allRequestResponses[0]['Response Headers'].location
              const parsedUrlObj = new URL(locationParam);
              const { sid, cshc } = parsedUrlObj.searchParams
              
              const frontdoorOptions = {
                method: 'GET',
                url: 'https://mindful-koala-78jg04-dev-ed.my.salesforce.com/secur/frontdoor.jsp',
                headers: {
                  'user-agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:89.0) Gecko/20100101 Firefox/89.0'
                },
                qs: {
                  sid,
                  cshc,
                  apv: 1,
                  allp: 1,
                  display: 'page',
                }
              }
              
              cy.request(frontdoorOptions)
            })
          
          cy.visit('https://mindful-koala-78jg04-dev-ed.lightning.force.com/lightning/setup/SetupOneHome/home')
          cy.get('.slds-truncate').first().should('contain', 'Setup')
      })
})