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