How to write effective test cases?

Start from one behavior per case: a single login, a single checkout path, or one permission rule. State preconditions clearly (user role, starting URL, test data) so anyone can run the case the same way twice and get the same result. Write steps as actions a person would take, then define an expected outcome that is observable - a message, a redirect, a record in the system, or visible UI state. Avoid vague expectations like “works correctly”; name what should be true when the case passes. Link each case to a requirement, user story, or risk so you know why it exists. Review cases when the feature changes and retire cases that no longer map to real user value. Good cases are short, repeatable, and easy to turn into automation later if needed.