@Test
public void test() throws Exception {

    // given
    List<Trace.Entry> entries = Lists.newArrayList();
    entries.add(Trace.Entry.newBuilder().setDepth(0).build());
    entries.add(Trace.Entry.newBuilder().setDepth(1).build());
    // when
    String json = TraceCommonService.entriesToJson(entries);
    // then
    assertThat(json).isEqualTo("[{\"startOffsetNanos\":0,\"durationNanos\":0,\"message\":\"\","
            + "\"childEntries\":[{\"startOffsetNanos\":0,\"durationNanos\":0,\"message\":\"\"}]"
            + "}]");
}