Preserve cookies / localStorage session across tests in Cypress

To update this thread, there is already a better solution available for preserving cookies (by @bkucera); but now there is a workaround available now to save and restore local storage between the tests (in case needed). I recently faced this issue; and found this solution working.

This solution is by using helper commands and consuming them inside the tests,

Inside - cypress/support/<some_command>.js

let LOCAL_STORAGE_MEMORY = {};

Cypress.Commands.add("saveLocalStorage", () => {
  Object.keys(localStorage).forEach(key => {
    LOCAL_STORAGE_MEMORY[key] = localStorage[key];
  });
});

Cypress.Commands.add("restoreLocalStorage", () => {
  Object.keys(LOCAL_STORAGE_MEMORY).forEach(key => {
    localStorage.setItem(key, LOCAL_STORAGE_MEMORY[key]);
  });
});

Then in test,

beforeEach(() => {
  cy.restoreLocalStorage();
});

afterEach(() => {
  cy.saveLocalStorage();
});

Reference: https://github.com/cypress-io/cypress/issues/461#issuecomment-392070888

From the Cypress docs

For persisting cookies: By default, Cypress automatically clears all cookies before each test to prevent state from building up.

You can configure specific cookies to be preserved across tests using the Cypress.Cookies api:

// now any cookie with the name 'session_id' will
// not be cleared before each test runs
Cypress.Cookies.defaults({
  preserve: "session_id"
})

NOTE: Before Cypress v5.0 the configuration key is "whitelist", not "preserve".

For persisting localStorage: It's not built in ATM, but you can achieve it manually right now because the method thats clear local storage is publicly exposed as Cypress.LocalStorage.clear.

You can backup this method and override it based on the keys sent in.

const clear = Cypress.LocalStorage.clear

Cypress.LocalStorage.clear = function (keys, ls, rs) {
  // do something with the keys here
  if (keys) {
    return clear.apply(this, arguments)
  }

}