Scala - unit test

Question

I would like to write unit test for this function, can any one help me with this?

    def train(sc: SparkContext, data: PreparedData): TopViewModel = {

    val itemStringIntMap = BiMap.stringInt(data.itemsView.keys)

    // collect Item as Map and convert ID to Int index
    val items: Map[Int, Item] = data.itemsView.map { 
        case (id, item) =>
        (itemStringIntMap(id), item)
    }.collectAsMap.toMap

    val topView = trainTopView(
        events = data.viewEvents,
        n = ap.n,
        itemStringIntMap = itemStringIntMap
    )
    logger.info(topView)

    new TopViewModel(
        topView = topView,
        itemStringIntMap = itemStringIntMap,
        items = items
    )
}

Thank you very much.