Regression Testing
Test that new code changes don't break existing functionality - critical after updates, bug fixes, and feature releases.
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What You'll Learn
Tutorial Contents
1.Regression Strategy
Test prioritization matrix: ``` Priority 1 Smoke tests (run on every deployment): Core user journeys that, if broken, block all users - User can register - User can log in - Core feature works (create, read, update) - Payment processes (sandbox)
Priority 2 Critical regression (run pre-release): Features used by most users / highest revenue impact - Search and filtering - Email notifications sent - Permissions and access control - Data export/import
Priority 3 Extended regression (weekly): Edge cases, admin features, low-traffic paths
Priority 4 Exploratory testing: Human testers exploring new features for unexpected behavior ```
When to run what:
``
On every PR: smoke tests (< 2 minutes)
On merge to main: smoke + critical (< 15 minutes)
Pre-release: full suite (can be 1-2 hours, run overnight)
Post-release: smoke tests against production
``
2.Automated Regression with Cypress
// cypress/support/commands.js reusable helpers
Cypress.Commands.add("login", (email = "test@example.com", password = "Pass@word1") => {
cy.request("POST", "/api/auth/login", { email, password })
.its("body.token")
.then((token) => {
window.localStorage.setItem("auth_token", token);
});
cy.visit("/dashboard");// cypress/e2e/regression/critical-flows.cy.js describe("Regression: Critical User Flows", () => { beforeEach(() => { cy.login(); });
it("user can create and view a project", () => { cy.get("[data-cy='new-project']").click(); cy.get("input[name='name']").type("Regression Test Project"); cy.get("[data-cy='create-submit']").click(); cy.url().should("include", "/projects/"); cy.contains("Regression Test Project").should("be.visible"); });
it("user can invite a team member", () => { cy.visit("/team"); cy.get("[data-cy='invite-btn']").click(); cy.get("input[name='email']").type("newmember@example.com"); cy.get("[data-cy='send-invite']").click(); cy.contains("Invitation sent").should("be.visible"); });
it("search returns relevant results", () => { cy.get("[data-cy='search-input']").type("regression"); cy.get("[data-cy='search-results']") .should("be.visible") .and("contain", "Regression Test Project"); });
// After a bug is fixed, add the test that would have caught it it("deleted projects do not appear in list", () => { // Regression for Bug #456: deleted projects were still shown cy.get("[data-cy='project-item']").first().as("project"); cy.get("@project").find("[data-cy='delete']").click(); cy.get("[data-cy='confirm-delete']").click(); cy.get("@project").should("not.exist"); }); }); ```
Code Example
// Regression test suite (Cypress)
describe('Regression Suite - Core Features', () => {
beforeEach(() => {
cy.visit('https://app.example.com');
cy.login('testuser@example.com', 'password');
});
// Critical user flows that should never break
it('User can create a new project', () => {
cy.contains('New Project').click();
cy.get('input[name="projectName"]').type('Test Project');
cy.contains('Create').click();
cy.contains('Test Project').should('be.visible');
});
it('User can upload a file', () => {
cy.get('input[type="file"]').attachFile('test.pdf');
cy.contains('Upload').click();
cy.contains('test.pdf').should('be.visible');
});
it('Dashboard loads and displays user data', () => {
cy.visit('/dashboard');
cy.get('.dashboard-header').should('be.visible');
cy.get('.stats-widget').should('have.length.greaterThan', 0);
});
it('Navigation menu works correctly', () => {
cy.get('[data-testid="nav-projects"]').click();
cy.url().should('include', '/projects');
cy.get('[data-testid="nav-settings"]').click();
cy.url().should('include', '/settings');
});
});Pro Tips
- 1Prioritize regression tests by business risk, not code coverage. A bug in checkout is a revenue disaster; a bug in the admin color theme is a nuisance.
- 2Run smoke tests (the 10 most critical paths) on every deployment, and full regression only before major releases.
- 3Tag your tests @smoke, @regression, @critical so CI can run the right suite at each pipeline stage.
- 4When a bug is found in production, write the test that would have caught it before fixing the bug. This prevents regression forever.
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