During which step should you ensure that the problem is fully resolved and that implementation did not create new issues?

The step where you ensure that the problem is fully resolved and that the implementation did not create new issues is the testing phase. During this step, you rigorously evaluate the solution to confirm that it addresses the initial problem effectively. This involves running multiple tests and scenarios to verify functionality and performance, ensuring that all aspects of the solution work as intended.

In the testing phase, potential side effects or new issues introduced by the implementation are also identified and addressed, which is crucial for maintaining system stability and integrity. It's an important quality assurance step that helps prevent future problems that could arise from the changes made, ensuring a robust and reliable solution.

This focus on validation is a key aspect of the testing process, distinguishing it from other phases, such as diagnosing or implementing the solution where the primary focus is on development rather than verification.