p.setAcquisitionContext(new AcquisitionContext(-1l));
AcquisitionContext ac = new AcquisitionContext(); ac.setId(-1l); p.setAcquisitionContext(ac);
    public void testUnloadedEntityFieldOnDetachedPixels() throws Exception    {        // PREPARE -------------------------------------------------        //      TODO or bool flag?        p.setAcquisitionContext(new AcquisitionContext(-1l));        _up.saveAndReturnObject(p);        flush();        clear();                // TEST -------------------------------------------------        assertNotNull("should be back.", p.getAcquisitionContext());        assertTrue("and it should have a valid id.", p.getAcquisitionContext()                .getId().longValue() > 0);    }