@Test
  public void testSetContentViaOutputStream() throws Exception {
    int attachLength = 20;
    int seed = (int) System.currentTimeMillis();
    final XWikiAttachment attach = new XWikiAttachment();
    final InputStream ris = new RandomInputStream(attachLength, seed);
    attach.setContent(ris);
    assertTrue(
        IOUtils.contentEquals(
            new RandomInputStream(attachLength, seed),
            attach.getAttachment_content().getContentInputStream()));
    // Now write to the attachment via an OutputStream.
    final XWikiAttachmentContent xac = attach.getAttachment_content();
    xac.setContentDirty(false);
    final OutputStream os = xac.getContentOutputStream();

    // Adding content with seed+1 will make a radically different set of content.
    IOUtils.copy(new RandomInputStream(attachLength, seed + 1), os);

    // It should still be the old content.
    assertTrue(
        IOUtils.contentEquals(
            new RandomInputStream(attachLength, seed), xac.getContentInputStream()));
    assertFalse(xac.isContentDirty());

    os.close();

    // Now it should be the new content.
    assertTrue(
        IOUtils.contentEquals(
            new RandomInputStream(attachLength, seed + 1), xac.getContentInputStream()));
    assertTrue(xac.isContentDirty());
  }