Is it possible to use Cypress e2e testing with a firebase auth project?

Question

I am exploring Cypress for e2e testing, looks like great software. The problem is Authentication, the Cypress documentation explains why using the UI is very bad here.

So

Answer 1

This is certainly a hack but to get around the login part for the app I am working on I use the beforeEach hook to login to the application.

beforeEach(() => {
  cy.resetTestDatabase().then(() => {
    cy.setupTestDatabase();
  });
});

Which is derived from my helper functions.

Cypress.Commands.add('login', () => {
  return firebase
    .auth()
    .signInWithEmailAndPassword(Cypress.env('USER_EMAIL'), Cypress.env('USER_PASSWORD'));
});

Cypress.Commands.add('resetTestDatabase', () => {
  return cy.login().then(() => {
    firebase
      .database()
      .ref(DEFAULT_CATEGORIES_PATH)
      .once('value')
      .then(snapshot => {
        const defaultCategories = snapshot.val();
        const updates = {};
        updates[TEST_CATEGORIES_PATH] = defaultCategories;
        updates[TEST_EVENTS_PATH] = null;
        updates[TEST_STATE_PATH] = null;
        updates[TEST_EXPORT_PATH] = null;

        return firebase
          .database()
          .ref()
          .update(updates);
      });
  });
});

What I would like to know is how the information coming back from firebase ultimately gets saved to localStorage. I don't really have an answer to this but it works. Also, the app uses .signInWithPopup(new firebase.auth.GoogleAuthProvider()) whereas above it signs in with email and password. So I am kind of shortcutting the signin process only because cypress has the CORS limitation.