What are the most important Cypress best practices?

Good Cypress tests share the same qualities as good tests anywhere: they are independent, deterministic, readable and focused on behaviour. Cypress adds specific tools for each of those, and the practices below use them rather than fighting them.

The practices that matter most

• Each test sets up its own state and does not depend on order
• Select with data-cy or accessible names, not CSS structure
• Wait for requests with intercept aliases, not fixed delays
• Use cy.session or API setup for login and other expensive setup
• Assert on what the user sees, not on internal state or implementation
• Keep specs focused so failures are easy to locate
• Treat a flaky test as a bug and fix the race rather than adding retries

describe("cart", () => {
  beforeEach(() => {
    cy.intercept("GET", "/api/cart").as("getCart");
    cy.visit("/cart");
    cy.wait("@getCart");
  });

  it("removes an item", () => {
    cy.get("[data-cy=cart-item]").should("have.length", 2);

    cy.get("[data-cy=cart-item]")
      .first()
      .find("[data-cy=remove]")
      .click();

    cy.get("[data-cy=cart-item]").should("have.length", 1);
  });
});

Prefer app actions for setup when the journey is not what you are testing, and keep assertions in the spec so failing output is readable. A common smell is a helper that performs five actions and three assertions; when it fails, nobody can tell which requirement broke.

Do not disable test isolation, add force clicks or raise global timeouts to get a suite green. Those changes treat symptoms. Fix the state or the wait at the point where the test actually depends on it.