@Test
public void invalidResourceType() {

    PDAcroForm mergeThis = new PDAcroForm(new PDDocument());
    PDResources dr = new PDResources();
    dr.getCOSObject().setInt(COSName.FONT, 10);
    mergeThis.setDefaultResources(dr);
    PDAcroForm intoThis = new PDAcroForm(new PDDocument());
    AcroFormUtils.mergeDefaults(mergeThis, intoThis);
    assertNull(intoThis.getDefaultResources().getCOSObject().getItem(COSName.FONT));
}