public static Header[] getStockHeaders(final Instant when) {
        return new Header[] {
                new BasicHeader("Date", DateUtils.formatStandardDate(when)),
                new BasicHeader("Server", "MockServer/1.0")
        };
    }
Generates a response body with random content.
 @param nbytes length of the desired response body
 @return an {@link HttpEntity}
httpclient5-cache/src/test/java/org/apache/hc/client5/http/impl/cache/HttpTestUtils.java