mocking multipart mime request with mockito

Question

I'm pretty new to Mockito and mocking out servlets for testing. I'm having problems mocking out an HttpServletRequest which sends some form data to my servlet as a MimeMultiPart. In my servlet I call request.getInputStream() as follows:

mimeMultiPart = new MimeMultipart(new ByteArrayDataSource(
                request.getInputStream(), Constants.MULTI_PART_FORM_DATA));

When I mock out my input stream I create an entire MimeMultiPart message and then I try to return a ServletInputStream from it in the code below

    //Helper function to create ServletInputStream
private ServletInputStream createServletInputStream(Object object)
        throws Exception {

    //create output stream
    ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
    ObjectOutputStream outStream = new ObjectOutputStream(byteOut);

    //this part no workey
    outStream.writeObject(object);

    //create input stream
    final InputStream byteIn = new ByteArrayInputStream(byteOut.toByteArray());

    //create a new ServletInputStream and return it
    return new ServletInputStream() {

        @Override
        public int read() throws IOException {
            return byteIn.read();
        }
    };
}

@Test
public void testDoPost() throws Exception {
    PrintWriter writer;
    writer = new PrintWriter("testSendMultiPartBatchResponse.txt");
    when(response.getWriter()).thenReturn(writer);

            //this is the mocked request
    when(request.getInputStream()).thenReturn(
            createServletInputStream(multiPartResponse));

. . . 

now when I run this test I receive the following error on outStream.writeObject(object):

java.io.NotSerializableException: javax.mail.internet.MimeMultipart
at java.io.ObjectOutputStream.writeObject0(Unknown Source)
at java.io.ObjectOutputStream.writeObject(Unknown Source)

    . . . 

it's not necessary to post the rest of the stack trace, I'm pretty sure the problem is that MimeMultiPart is not serializable, but I don't know how to rectify this. Is there another way to mock out the request? I am at a loss :(

Answer 1

I think this should work:

final ByteArrayOutputStream os = new ByteArrayOutputStream ();
multiPartResponse.writeTo (os);
final ByteArrayInputStream is = new ByteArrayInputStream (os.toByteArray ());
when(request.getInputStream()).thenReturn(new ServletInputStream() {
        @Override
        public int read() throws IOException {
            return is.read();
        }
    });