### Question:
ResponseHeadersConfigurer { final Map<String, String> getHeadersMap() { return Collections.unmodifiableMap(headersMap); } ResponseHeadersConfigurer();  ResponseHeadersConfigurer(final String headersAsString); static ResponseHeadersConfigurer noCache(); static ResponseHeadersConfigurer emptyHeaders(); static ResponseHeadersConfigurer fromConfig(final WroConfiguration config); static ResponseHeadersConfigurer withHeadersSet(final String headersAsString); void configureDefaultHeaders(final Map<String, String> map); void setHeaders(final HttpServletResponse response); Long getLastModifiedTimestamp();  }### Answer:
@Test public void shouldUseConfiguredDefaultHeaders() { final String etag = "123"; victim = new ResponseHeadersConfigurer() { @Override public void configureDefaultHeaders(final Map<String, String> map) { map.put(HttpHeader.ETAG.name(), etag); } }; final Map<String, String> map = victim.getHeadersMap(); assertEquals(1, map.size()); assertEquals(etag, map.get(HttpHeader.ETAG.getHeaderName())); }