@Test
public void testMergeHeadersEmpty() {

  Map<String, List<String>> headers1 = createHeaders();
  Map<String, List<String>> headers2 = createHeaders("key1", "value1", "key2", "value2");
  Map<String, List<String>> mergedHeaders = Headers.mergeHeaders(headers1, headers2);
  Map<String, List<String>> expectedHeaders = createHeaders("key1", "value1", "key2", "value2");
  assertThat(mergedHeaders).containsExactlyEntriesIn(expectedHeaders);
}