cypress_salesforce_oauth_login.js

const { SF_username, SF_password, SF_client_id, SF_client_secret, SF_security_token } = Cypress.env()

describe('Programmatically log in to SF app', () => {
    
  it('makes XHR req & loads dashboard', () => {
      Cypress.log({name: 'loginViaOAuth'});
      
      // request access token from SF OAuth endpoint
      const oAuthTokenOptions = {
        method: 'POST',
        url: 'https://login.salesforce.com/services/oauth2/token',
        body: {
          grant_type: "password",
          client_id: SF_client_id,
          client_secret: SF_client_secret,
          username: SF_username,
          password: `${SF_password}${SF_security_token}`
        },
        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'
        }
      }

      cy.request(oAuthTokenOptions)
        .then(({ body }) => {
          const { access_token, instance_url } = body
          // Add access_token as "sid" to "secur/frontdoor.jsp" per community suggestion
          // https://github.com/cypress-io/cypress/issues/2367#issuecomment-584058927
          cy.request(`${instance_url}/secur/frontdoor.jsp?sid=${access_token}`)
          
          cy.setCookie('sid', access_token, {
            "path": "/",
            "secure": true,
            "httpOnly": false,
            "domain": "mindful-koala-78jg04-dev-ed.lightning.force.com",
            "sameSite": "no_restriction"
          })
          
          cy.visit(`${instance_url}/lightning/page/home`)
       })
    })
})