[Java][GAE][Mockito] testing servlet requests/responses

gistfile1.java

import static org.junit.Assert.*;
import static org.junit.matchers.JUnitMatchers.*;  // for non-hamcrest core matchers
import static org.mockito.Mockito.*;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.junit.Before;
import org.junit.Test;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;

public class MyServletTest {

	private MyServlet servlet;
	private HttpServletRequest request;
	private HttpServletResponse response;
	private StringWriter response_writer;
	private Map<String, String> parameters;

	@Before
	public void setUp() throws IOException {
		parameters = new HashMap<String, String>();
		servlet = new MyServlet();
		request = mock(HttpServletRequest.class);
		response = mock(HttpServletResponse.class);
		response_writer = new StringWriter();

		when(request.getParameter(anyString())).thenAnswer(new Answer<String>() {
			public String answer(InvocationOnMock invocation) {
				return parameters.get((String) invocation.getArguments()[0]);
			}
		});
		when(response.getWriter()).thenReturn(new PrintWriter(response_writer));
	}

	@Test
	public void testPost1() throws Exception {
		parameters.put("param1", "some value");
		servlet.doPost(request, response);
		assertThat(response_writer.toString(),
			// a non-hamcrest core matcher
			containsString("i'm only looking for this in the bloody long response"));
	}

}