Automated testing is - arguably - one of the surest ways to maintain quality in a project, although it is fair to say that it will not solve all problems. Even a simple web application or online store benefits from automation: regressions are detected more quickly, and errors are less likely to reach the user. On the other hand, you have to reckon with the cost of maintaining tests and their sometimes unreliable nature.
You'll learn how to build a meaningful testing strategy from scratch. Short unit tests that check single functions - for example, email address validation or tax calculations - are great for quick verification. Integration tests will show whether modules work together, such as gateway payment and database enrollment. And end-to-end tests simulate user behavior: logging in, adding to cart and finalizing an order. Each of these types has its place, although sometimes it's worth leaving exploratory tests performed manually as well.
We will describe practical tools and scenarios for their use. Jest (Jest, Mocha) for JavaScript, PyTest for Python, PHPUnit for PHP; Selenium and Cypress for browser testing, Postman for API. We will show which tool will work for interface testing and which for API testing.
Automation is not just about scripts. CI/CD runs tests with every commit, coverage reports suggest which pieces need attention, and performance monitoring helps detect problems before they reach users. In my experience, a well-crafted process combines these elements and - perhaps somewhat obviously - requires constant adjustment as applications change.