Items created by Loader never destroyed when used from QtTest

import QtQuick 2.0
import QtTest 1.0

Item {
    property int itemCount: 0

    Loader { id: loader }

    Component {
        id: item
        Item {
            Component.onCompleted: { console.log("item created"); itemCount++ }
            Component.onDestruction: { console.log("item destroyed"); itemCount-- }
        }
    }

    resources: TestCase {
        name: "URL"

        function test_loader() {
            for (var i = 0; i < 5; i++) {
                loader.sourceComponent = item
                wait(100)
                console.log("itemCount: " + itemCount)
                verify(itemCount == 1)
                loader.sourceComponent = null
                wait(100)
                console.log("itemCount: " + itemCount)
                verify(itemCount == 0)
            }
        }
    }
}