Software development process

Process models

• Waterfall: strict sequential phases (requirements → design → build → test → maintain). Simple, but slow to absorb change.
• Agile / Scrum: short iterations (*sprints*) deliver working software early and welcome changing requirements.
• Spiral: iterative loops, each beginning with heavy risk analysis.

Testing levels

• Unit — a single module in isolation.
• Integration — modules working together.
• System — the whole product against its requirements.
• Acceptance — the user confirms it meets their needs.

Black-box vs white-box

• Black-box: test behaviour against the spec, ignoring the internals.
• White-box: design tests from the internal code paths and logic.