Verification vs Validation

// ── VERIFICATION: Does it match the spec? ─────────────────────

// Spec: "Maximum file upload size = 10 MB"
// Verification test - does code enforce exactly 10 MB?
test("rejects files over 10MB", async () => {
    const file11MB = generateFile(11 * 1024 * 1024);  // 11MB file
    const res = await uploadFile(file11MB);
    expect(res.status).toBe(413);  // 413 = Payload Too Large
});

test("accepts files exactly at 10MB limit", async () => {
    const file10MB = generateFile(10 * 1024 * 1024);
    const res = await uploadFile(file10MB);
    expect(res.status).toBe(200);
});
// If these pass: verification ✅ - code matches spec

// ── VALIDATION: Does it meet USER needs? ──────────────────────

// User research reveals: average user uploads profile photos = 2-3MB.
// But video testimonials = 80MB. Users NEED to upload large files.
// Despite verification passing, the product FAILS validation.

// Validation discovered via:
// - User acceptance testing (UAT) sessions
// - Beta user feedback: "I can't upload my product video!"  
// - Analytics: 42% of upload attempts fail (files > 10MB)

// Fix: Raise limit to 100MB for video-type files
// Now both verification AND validation are satisfied.

// ── Classic V&V Failure: NASA Mars Climate Orbiter (1999) ──────
// Verification ✅: Software correctly implemented the specification
// Validation ❌: Specification had wrong units (pounds-force vs. newtons)
// Result: $327M spacecraft destroyed on Mars arrival
// Lesson: Validating the spec itself is as important as validating the code