@Test
public void testLog_fieldsOnly_messageProvided() {

    Map<String, String> fields = new HashMap<>();
    fields.put(LOG_KEY_MESSAGE, "my-key-message");
    fields.put("foo", "bar");
    Span result = undertest.log(fields);
    assertSame(result, undertest);
    assertEquals(1, grpcSpan.getLogsCount());
    Log logRecord = grpcSpan.getLogs(0);
    Map<String, String> fieldMap = getLogFieldMap(logRecord);
    assertEquals("my-key-message", fieldMap.get(LOG_KEY_MESSAGE));
    assertEquals("bar", fieldMap.get("foo"));
    assertNotNull(logRecord.getTimestamp());
}