Which of the following is not a key issue stressed by an agile philosophy of software engineering?

Explanation

The Agile Manifesto and its twelve principles stress self-organizing teams, close customer collaboration, welcoming changing requirements even late in development, and frequent delivery of working software — so options 1, 2 and 3 are all genuine agile values. Agile deliberately rejects a long, separate testing stage bolted on after construction; testing is continuous and integrated into every iteration through practices such as test-driven development and continuous integration. A distinct build-then-test phase belongs to the plan-driven waterfall style, not to agile. Hence having a separate testing phase after a build phase is the odd one out.