[
  {
    "part_number": "test-optical",
    "kind": "optical",
    "propagation_delay_ns": 500.0,
    "price": 20.0,
    "source": "fixture"
  },
  {
    "part_number": "test-inductive-pickup",
    "kind": "inductive",
    "propagation_delay_ns": 0.0,
    "price": 5.0,
    "source": "fixture",
    "sensitivity_v_per_mps": 0.02,
    "threshold_v": 0.1
  }
]