{
    "medialib": [
        {
            "A/artist": "correct artist",
            "B/artist": "wrong artist",
            "A/title": "correct title",
            "B/title": "wrong title"
        }
    ],
    "collection": {
        "type": "universe"
    },
    "specification": {
        "type": "cluster-dict",
        "cluster-by": "value",
        "cluster-field": "artist",
        "source-preference": ["A"],
        "data": {
            "type": "metadata",
            "get": ["value"],
            "fields": ["title"]
        }
    },
    "expected": {
        "result": {
            "correct artist": "correct title"
        }
    }
}

Add a test for source-pref inheritance.
FEATURE(2477): Add a test for source-pref inheritance.
