{
  "id": "04-zero-cache-write",
  "description": "Zero cache write — 10xDEV must be null. Other metrics are defined if their denominators are non-zero.",
  "input": {
    "telemetry": { "input": 1000, "output": 5000, "cache_write": 0, "cache_read": 3000 },
    "source": { "provider": "test", "model": "test", "tool": "test" }
  },
  "expected": {
    "metrics": { "yield": 15.0, "leverage": 3.0, "velocity": 5.0, "snr": 0.8333, "dev10x": null },
    "warnings": ["dev10x_undefined: requires all four pillars > 0"]
  }
}