In what cases should a tester participate in the development and testing process of a project?

A tester should participate in the development and testing process of the project from the very beginning to:

• Understand requirements and specifications, which helps create relevant test cases.
• Detect defects early, reducing the cost of fixing them.
• Discuss architecture and potential risks together with developers.
• Automate tests in parallel with development, if provided.

Thus, the tester's involvement at all stages improves product quality and accelerates release.