object.setContentType("text");
object.getData().setData(content.getBytes());
// mock ByteStreamManager
ByteStreamManager byteStreamManager = mock(ByteStreamManager.class);
when(byteStreamManager.load("pid")).thenReturn(content.getBytes());
// execute test
DigitalObjectManager digitalObjectManager = new DigitalObjectManager();
digitalObjectManager.setByteStreamManager(byteStreamManager);
DigitalObject resultObject = digitalObjectManager.getCopyOfDataFilledDigitalObject(object);