@Test
public void testLog_nullMapValue() {

    Map<String, String> fields = new HashMap<>();
    fields.put("mykey1", null);
    Span result = undertest.log(fields);
    Log logRecord = grpcSpan.getLogs(0);
    Map<String, String> fieldMap = getLogFieldMap(logRecord);
    assertEquals("", fieldMap.get("mykey1"));
}