@Test
public void testLog_nullMapKey() {

    Map<String, String> fields = new HashMap<>();
    fields.put(null, "myvalue1");
    Span result = undertest.log(fields);
    Log logRecord = grpcSpan.getLogs(0);
    Map<String, String> fieldMap = getLogFieldMap(logRecord);
    assertEquals(null, fieldMap.get(null));
}