@Test
public void testRetrieveTagHeader() {

    ZMSFileChangeLogStoreCommon fstore = new ZMSFileChangeLogStoreCommon(FSTORE_PATH);
    Map<String, List<String>> responseHeaders = new HashMap<>();
    assertNull(fstore.retrieveTagHeader(responseHeaders));
    // add a header but not the tag one
    responseHeaders.put("Content-Type", Collections.singletonList("application/json"));
    responseHeaders.put("Content-Length", Collections.singletonList("10000"));
    assertNull(fstore.retrieveTagHeader(responseHeaders));
    // now add the tag header
    responseHeaders.put("tag", Arrays.asList("tag1", "tag2"));
    assertEquals(fstore.retrieveTagHeader(responseHeaders), "tag1");
}