This is a testharness.js-based test.
FAIL Test IDL implementation of Magnetometer Sensor promise_test: Unhandled rejection with value: object "Got an error before parsing any named definition: Unrecognised tokens, line 1 (tokens: "{\"error\": {\"message\"")
[
    {
        "type": "{",
        "value": "{",
        "trivia": ""
    },
    {
        "type": "string",
        "value": "\"error\"",
        "trivia": ""
    },
    {
        "type": ":",
        "value": ":",
        "trivia": ""
    },
    {
        "type": "{",
        "value": "{",
        "trivia": " "
    },
    {
        "type": "string",
        "value": "\"message\"",
        "trivia": ""
    }
]"
Harness: the test ran to completion.