At what point do you start writing test cases?

Test cases are started as early as possible in the development process, preferably during the planning stage or immediately after requirements are written. This helps:

• Clearly define what exactly needs to be tested.
• Ensure coverage of all usage scenarios.
• Allows the use of approaches like TDD (Test-Driven Development), where tests are written before the code.

If test cases are written after implementation, there is a risk of missing important checks or facing difficulties in reproducing bugs.

Ideally:

• During requirements analysis, test cases are created for positive and negative scenarios.
• Tests are updated or supplemented when functionality changes.

This approach improves product quality and facilitates test automation.