How can I execute code before all tests suite with Cypress?

In Cypress, to execute public code before all tests run, we typically use the before or beforeEach hooks. The before hook executes once before all tests in the test file run, while the beforeEach hook executes before each test case runs.

Here's an example:

If you want to execute certain code only once before all tests, you can use the before hook at the top level of the test file:

javascript
// Executes once before all tests
before(() => {
  // Place your public code here, such as:
  // Login operation
  cy.login('username', 'password'); // Assuming you have a wrapped login command
  // Set up test data or environment
  cy.setupTestData();
});

If you need to execute code before each test case, use the beforeEach hook:

javascript
// Executes before each test case
beforeEach(() => {
  // Place your public code here, such as:
  // Ensure starting from the login page each time
  cy.visit('/login'); // Visit the login page
  // You may need to clear browser's localStorage or cookies
  cy.clearLocalStorage();
  cy.clearCookies();
  // Initialization operations needed for each test case
  cy.initializeTestContext();
});

These hooks should be placed at the top of your test file, typically outside or inside the describe block that defines the test suite. Placing them outside the describe block means they run before all describe blocks defined in the file. Placing them inside affects only the test cases within that describe block.

Additionally, if you have multiple test files and want some code to run once before each test file, you can use the index.js file in Cypress's support folder. Code placed there runs before each test file executes.

For example, in cypress/support/index.js:

javascript
// Executes once before each test file
before(() => {
  // Public initialization code, such as setting API server state
  cy.initializeApiServer();
});

// Executes before each test case in each test file
beforeEach(() => {
  // Common logic before each test case, such as login
  cy.loginToApplication();
});

Remember to pay attention to the scope and execution order of these hooks to ensure the test environment is correctly set up.