On what basis do you write test cases and test scenarios?

Test cases and test scenarios are written based on the following artifacts and sources:

• Product requirements (Functional and Non-functional) — specifications describing what the system should do.
• Technical documentation — architecture, design, API specifications.
• User stories and acceptance criteria — user stories with acceptance criteria.
• Business processes and usage scenarios — real user operation scenarios.
• Risk analysis results — to focus on critical areas.

For example, from the user story "The user can log in with valid credentials," a test case is formed with steps to verify successful login and negative scenarios with incorrect password.

Thus, test cases reflect requirements and usage scenarios, ensuring the system meets expectations.