@Test
public void testToJson() {

    LOG.info("testToJson");
    Assert.assertEquals(
            "{\"gpsTracePoints\":[]}",
            TestUtils.replaceUniques(x.toJson()));
    Assert.assertEquals(
            "{\"gpsTracePoints\":[{\"time\":@DATETIME,\"position\":{\"lat\":1.0,\"lon\":2.0}}]}",
            TestUtils.replaceUniques(y.toJson()));
}