Having been asked how to unit test a servlet without using a container,
so much lately, I thought an example here might help - certainly should
help if the search engines pick it up.

Regards

Andrew

The servlet to test...

package org.amd.sandbox;

import java.io.IOException;
import java.io.PrintWriter;

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

public class HelloServlet extends HttpServlet {
 public void doGet (HttpServletRequest req,
                    HttpServletResponse res)
   throws ServletException, IOException
 {
   PrintWriter out = res.getWriter();

   out.print("Hello, world!");
   out.close();
 }
}

The Unit Test....

package org.amd.sandbox;

import java.io.PrintWriter;
import java.io.StringWriter;

import javax.servlet.http.HttpServletResponse;

import junit.framework.TestCase;

public class HelloServletTest extends TestCase {

 public void testDoGetSaysHello() throws Exception {
   StringWriter out = new StringWriter();

   HttpServletResponse res = new MockResponse(out);
   HelloServlet servlet = new HelloServlet();

   servlet.doGet(null, res);

   assertEquals("Hello, world!", out.toString());
 }

}

Two helper classes......

Andrew

The servlet to test...

package org.amd.sandbox;

import java.io.IOException;
import java.io.PrintWriter;

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

public class HelloServlet extends HttpServlet {
 public void doGet (HttpServletRequest req,
                    HttpServletResponse res)
   throws ServletException, IOException
 {
   PrintWriter out = res.getWriter();

   out.print("Hello, world!");
   out.close();
 }
}

The Unit Test....

package org.amd.sandbox;

import java.io.PrintWriter;
import java.io.StringWriter;

import javax.servlet.http.HttpServletResponse;

class MockResponse extends HttpServletResponseAdapter {

 private StringWriter out;

 public MockResponse(StringWriter stringWriter) {
   out = stringWriter;
 }

 public PrintWriter getWriter() {
   return new PrintWriter(out);
 }

}

The following class was auto generated by Eclipse - Its purpose is to
provide a simple implementation of the HttpServletResponse interface
and its methods are purposely left as shown below.  Its the purpose of
the deriving class MockResponse,  above that over rides all methods
that are needed by the current unit test.

Obviously, the more correctly implemented methods required by further
unit tests, means extending the current MockResponse class.

package org.amd.sandbox;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletResponse;

public class HttpServletResponseAdapter implements HttpServletResponse
{

 public void addCookie(Cookie arg0) {
   throw new RuntimeException("HttpServletResponseAdapter.addCookie()
not yet implemented - faked for unit tests");
 }

 public boolean containsHeader(String arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.containsHeader() not yet
implemented - faked for unit tests");
 }

 public String encodeURL(String arg0) {
   throw new RuntimeException("HttpServletResponseAdapter.encodeURL()
not yet implemented - faked for unit tests");
 }

 public String encodeRedirectURL(String arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.encodeRedirectURL() not
yet implemented - faked for unit tests");
 }

 public String encodeUrl(String arg0) {
   throw new RuntimeException("HttpServletResponseAdapter.encodeUrl()
not yet implemented - faked for unit tests");
 }
 public String encodeRedirectUrl(String arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.encodeRedirectUrl() not
yet implemented - faked for unit tests");
 }

 public void sendError(int arg0, String arg1) throws IOException {
   throw new RuntimeException("HttpServletResponseAdapter.sendError()
not yet implemented - faked for unit tests");
 }

 public void sendError(int arg0) throws IOException {
   throw new RuntimeException("HttpServletResponseAdapter.sendError()
not yet implemented - faked for unit tests");
 }

 public void sendRedirect(String arg0) throws IOException {
   throw new
RuntimeException("HttpServletResponseAdapter.sendRedirect() not yet
implemented - faked for unit tests");
 }

 public void setDateHeader(String arg0, long arg1) {
   throw new
RuntimeException("HttpServletResponseAdapter.setDateHeader() not yet
implemented - faked for unit tests");
 }
 public void addDateHeader(String arg0, long arg1) {
   throw new
RuntimeException("HttpServletResponseAdapter.addDateHeader() not yet
implemented - faked for unit tests");
 }
 public void setHeader(String arg0, String arg1) {
   throw new RuntimeException("HttpServletResponseAdapter.setHeader()
not yet implemented - faked for unit tests");
 }

 public void addHeader(String arg0, String arg1) {
   throw new RuntimeException("HttpServletResponseAdapter.addHeader()
not yet implemented - faked for unit tests");
 }
 public void setIntHeader(String arg0, int arg1) {
   throw new
RuntimeException("HttpServletResponseAdapter.setIntHeader() not yet
implemented - faked for unit tests");
 }

 public void addIntHeader(String arg0, int arg1) {
   throw new
RuntimeException("HttpServletResponseAdapter.addIntHeader() not yet
implemented - faked for unit tests");
 }

 public void setStatus(int arg0) {
   throw new RuntimeException("HttpServletResponseAdapter.setStatus()
not yet implemented - faked for unit tests");
 }

 public void setStatus(int arg0, String arg1) {
   throw new RuntimeException("HttpServletResponseAdapter.setStatus()
not yet implemented - faked for unit tests");
 }
 public String getCharacterEncoding() {
   throw new
RuntimeException("HttpServletResponseAdapter.getCharacterEncoding() not
yet implemented - faked for unit tests");
 }

 public String getContentType() {
   throw new
RuntimeException("HttpServletResponseAdapter.getContentType() not yet
implemented - faked for unit tests");
 }

 public ServletOutputStream getOutputStream() throws IOException {
   throw new
RuntimeException("HttpServletResponseAdapter.getOutputStream() not yet
implemented - faked for unit tests");
 }

 public PrintWriter getWriter() throws IOException {
   throw new RuntimeException("HttpServletResponseAdapter.getWriter()
not yet implemented - faked for unit tests");
 }

 public void setCharacterEncoding(String arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.setCharacterEncoding() not
yet implemented - faked for unit tests");
 }

 public void setContentLength(int arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.setContentLength() not yet
implemented - faked for unit tests");
 }
 public void setContentType(String arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.setContentType() not yet
implemented - faked for unit tests");
 }
 public void setBufferSize(int arg0) {
   throw new
RuntimeException("HttpServletResponseAdapter.setBufferSize() not yet
implemented - faked for unit tests");
 }
 public int getBufferSize() {
   throw new
RuntimeException("HttpServletResponseAdapter.getBufferSize() not yet
implemented - faked for unit tests");
 }

 public void flushBuffer() throws IOException {
   throw new
RuntimeException("HttpServletResponseAdapter.flushBuffer() not yet
implemented - faked for unit tests");
 }
 public void resetBuffer() {
   throw new
RuntimeException("HttpServletResponseAdapter.resetBuffer() not yet
implemented - faked for unit tests");
 }

 public boolean isCommitted() {
   throw new
RuntimeException("HttpServletResponseAdapter.isCommitted() not yet
implemented - faked for unit tests");
 }

 public void reset() {
   throw new RuntimeException("HttpServletResponseAdapter.reset() not
yet implemented - faked for unit tests");
 }

 public void setLocale(Locale arg0) {
   throw new RuntimeException("HttpServletResponseAdapter.setLocale()
not yet implemented - faked for unit tests");
 }

 public Locale getLocale() {
   throw new RuntimeException("HttpServletResponseAdapter.getLocale()
not yet implemented - faked for unit tests");
 }

}