rebase with latest changes

18 files changed, 507 insertions, 156 deletions

diff --git a/.travis.yml b/.travis.yml
index d362005..8ad6c5f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,8 +9,9 @@ env:
 
 # command to install dependencies
 install:
+  - pip install tornado
   - pip install git+https://github.com/FOSSEE/online_test.git#egg=yaksh-0.1
-  - pip install -q Django==$DJANGO --use-mirrors
+  - pip install -q Django==$DJANGO
   - pip install -q pytz==2016.4
   - pip install -q python-social-auth==0.2.19
 
@@ -20,4 +21,4 @@ before_install:
 
 # command to run tests
 script:
-  - python manage.py test yaksh
+  - python manage.py test -v 2 yaksh
diff --git a/requirements.txt b/requirements.txt
index 5438d8a..bea0017 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,3 +3,4 @@ mysql-python==1.2.5
 django-taggit==0.18.1
 pytz==2016.4
 python-social-auth==0.2.19
+tornado
diff --git a/yaksh/admin.py b/yaksh/admin.py
index ddd5e62..b5c8933 100644
--- a/yaksh/admin.py
+++ b/yaksh/admin.py
@@ -1,9 +1,11 @@
-from yaksh.models import Question, Quiz
-from yaksh.models import TestCase, StandardTestCase, StdioBasedTestCase
+from yaksh.models import Question, Quiz, QuestionPaper
+from yaksh.models import TestCase, StandardTestCase, StdioBasedTestCase, Course
 from django.contrib import admin
 
 admin.site.register(Question)
 admin.site.register(TestCase)
 admin.site.register(StandardTestCase)
 admin.site.register(StdioBasedTestCase)
+admin.site.register(Course)
 admin.site.register(Quiz)
+admin.site.register(QuestionPaper)
diff --git a/yaksh/code_server.py b/yaksh/code_server.py
index 2d8567e..e19e9c8 100755
--- a/yaksh/code_server.py
+++ b/yaksh/code_server.py
@@ -1,9 +1,11 @@
 #!/usr/bin/env python
-"""This server runs an XMLRPC server that can be submitted code and tests
-and returns the output.  It *should* be run as root and will run as the user
-'nobody' so as to minimize any damange by errant code.  This can be configured
-by editing settings.py to run as many servers as desired.  One can also
-specify the ports on the command line.  Here are examples::
+
+"""This server runs an HTTP server (using tornado) and several code servers
+using XMLRPC that can be submitted code
+and tests and returns the output.  It *should* be run as root and will run as
+the user 'nobody' so as to minimize any damange by errant code.  This can be
+configured by editing settings.py to run as many servers as desired.  One can
+also specify the ports on the command line.  Here are examples::
 
   $ sudo ./code_server.py
   # Runs servers based on settings.py:SERVER_PORTS one server per port given.
@@ -17,18 +19,32 @@ All these servers should be running as nobody.  This will also start a server
 pool that defaults to port 50000 and is configurable in
 settings.py:SERVER_POOL_PORT.  This port exposes a `get_server_port` function
 that returns an available server.
+
 """
-import sys
+
+# Standard library imports
 from SimpleXMLRPCServer import SimpleXMLRPCServer
-import pwd
+import json
+from multiprocessing import Process, Queue
 import os
-import stat
 from os.path import isdir, dirname, abspath, join, isfile
+import pwd
+import re
 import signal
-from multiprocessing import Process, Queue
+import stat
 import subprocess
-import re
-import json
+import sys
+
+try:
+    from urllib import unquote
+except ImportError:
+    # The above import will not work on Python-3.x.
+    from urllib.parse import unquote
+
+# Library imports
+from tornado.ioloop import IOLoop
+from tornado.web import Application, RequestHandler
+
 # Local imports.
 from settings import SERVER_PORTS, SERVER_POOL_PORT
 from language_registry import create_evaluator_instance, unpack_json
@@ -62,7 +78,7 @@ class CodeServer(object):
         """Calls relevant EvaluateCode class based on language to check the
          answer code
         """
-        code_evaluator = create_evaluator_instance(language, 
+        code_evaluator = create_evaluator_instance(language,
             test_case_type,
             json_data,
             in_dir
@@ -104,15 +120,30 @@ class ServerPool(object):
         """
         self.my_port = pool_port
         self.ports = ports
-        queue = Queue(maxsize=len(ports))
+        queue = Queue(maxsize=len(self.ports))
         self.queue = queue
         servers = []
-        for port in ports:
+        processes = []
+        for port in self.ports:
             server = CodeServer(port, queue)
             servers.append(server)
             p = Process(target=server.run)
-            p.start()
+            processes.append(p)
         self.servers = servers
+        self.processes = processes
+        self.app = self._make_app()
+
+    def _make_app(self):
+        app = Application([
+            (r"/.*", MainHandler, dict(server=self)),
+        ])
+        app.listen(self.my_port)
+        return app
+
+    def _start_code_servers(self):
+        for proc in self.processes:
+            if proc.pid is None:
+                proc.start()
 
     # Public Protocol ##########
 
@@ -120,36 +151,63 @@ class ServerPool(object):
         """Get available server port from ones in the pool.  This will block
         till it gets an available server.
         """
-        q = self.queue
-        was_waiting = True if q.empty() else False
-        port = q.get()
-        if was_waiting:
-            print '*'*80
-            print "No available servers, was waiting but got server \
-                   later at %d." % port
-            print '*'*80
-            sys.stdout.flush()
-        return port
+        return self.queue.get()
+
+    def get_status(self):
+        """Returns current queue size and total number of ports used."""
+        try:
+            qs = self.queue.qsize()
+        except NotImplementedError:
+            # May not work on OS X so we return a dummy.
+            qs = len(self.ports)
+
+        return qs, len(self.ports)
 
     def run(self):
         """Run server which returns an available server port where code
         can be executed.
         """
-        server = SimpleXMLRPCServer(("0.0.0.0", self.my_port))
+        # We start the code servers here to ensure they are run as nobody.
+        self._start_code_servers()
+        IOLoop.current().start()
+
+    def stop(self):
+        """Stop all the code server processes.
+        """
+        for proc in self.processes:
+            proc.terminate()
+        IOLoop.current().stop()
+
+
+class MainHandler(RequestHandler):
+    def initialize(self, server):
         self.server = server
-        server.register_instance(self)
-        server.serve_forever()
+
+    def get(self):
+        path = self.request.path[1:]
+        if len(path) == 0:
+            port = self.server.get_server_port()
+            self.write(str(port))
+        elif path == "status":
+            q_size, total = self.server.get_status()
+            result = "%d servers out of %d are free.\n"%(q_size, total)
+            load = float(total - q_size)/total*100
+            result += "Load: %s%%\n"%load
+            self.write(result)
 
 
 ###############################################################################
 def main(args=None):
-    run_as_nobody()
     if args:
-        ports = [int(x) for x in args[1:]]
+        ports = [int(x) for x in args]
     else:
         ports = SERVER_PORTS
 
     server_pool = ServerPool(ports=ports, pool_port=SERVER_POOL_PORT)
+    # This is done *after* the server pool is created because when the tornado
+    # app calls listen(), it cannot be nobody.
+    run_as_nobody()
+
     server_pool.run()
 
 if __name__ == '__main__':
diff --git a/yaksh/documentation/installation.rst b/yaksh/documentation/installation.rst
index 4acee61..51efea7 100644
--- a/yaksh/documentation/installation.rst
+++ b/yaksh/documentation/installation.rst
@@ -64,4 +64,52 @@ This starts the code server
 
 **And entering the following admin credentials**
 	* Username: admin
-	* Password: admin
\ No newline at end of file
+	* Password: admin
+
+Running The Code Server
+-----------------------
+
+**Local Instance**:
+
+In a new terminal run the command::
+
+	sudo python /path/to/code_server.py
+
+Keep this instance running in the background
+
+**Using Docker**:
+
+1. Install docker 
+
+2. Create a Docker Image using the Docker file:
+
+	* Go to the directory where the project is located::
+
+		cd /path/to/online_test
+
+	* Build a docker image using the Dockerfile::
+
+		sudo docker build --tag=yaksh_code_server:v1 .
+
+3. Start a Docker container::
+
+		docker run -d -p 8001:8001 -p 53579:53579 -v /path/to/online_test/yaksh/output:/src/yaksh/output yaksh_code_server:v1
+
+**Note**:
+	* The default ports on which the code server runs and the pool port on which the former ports are available is specified in online_test/yaksh/settings.py. The code server also supports multiple ports
+
+	* The server port is 8001 by default, this can be changed in the settings::
+	
+		SERVER_PORTS = 8001
+
+	* Multiple ports can be specified as::
+	
+		SERVER_PORTS = [8001, 8002, 8003, 8004, 8005] # Or use range(8001, 8040) for larger number of ports
+
+	* The default pool port is 53579 by default, this can be changed in the settings::
+	
+		SERVER_POOL_PORT = 53579
+
+	* The docker command to start a docker container when using multiple ports is::
+	
+		docker run -d -p 8001-8039:8001-8039 -p 53579:53579 yaksh_code_server:v1
diff --git a/yaksh/models.py b/yaksh/models.py
index bdd3875..d2bffbe 100644
--- a/yaksh/models.py
+++ b/yaksh/models.py
@@ -570,7 +570,9 @@ class QuestionPaper(models.Model):
         if self.quiz.has_prerequisite():
             prerequisite = self._get_prequisite_paper()
             return prerequisite._is_questionpaper_passed(user)
-
+    
+    def __unicode__(self):
+        return "Question Paper for " + self.quiz.description
 
 ###############################################################################
 class QuestionSet(models.Model):
@@ -784,21 +786,28 @@ class AnswerPaper(models.Model):
             Adds the completed question to the list of answered
             questions and returns the next question.
         """
+        next_question = self.next_question(question_id)
         self.questions_answered.add(question_id)
         self.questions_unanswered.remove(question_id)
+        if next_question.id == int(question_id):
+            return None
+        return next_question
 
-        return self.current_question()
-
-    def skip(self, question_id):
+    def next_question(self, question_id):
         """
             Skips the current question and returns the next sequentially
              available question.
         """
-        questions = self.questions_unanswered.all()
-        question_cycle = cycle(questions)
-        for question in question_cycle:
-            if question.id==int(question_id):
-                return question_cycle.next()
+        unanswered_questions = self.questions_unanswered.all()
+        questions = list(unanswered_questions.values_list('id', flat=True))
+        if len(questions) == 0:
+            return None
+        try:
+            index =  questions.index(int(question_id))
+            next_id = questions[index+1]
+        except (ValueError, IndexError):
+            next_id = questions[0]
+        return unanswered_questions.get(id=next_id)
 
     def time_left(self):
         """Return the time remaining for the user in seconds."""
diff --git a/yaksh/templates/user.html b/yaksh/templates/user.html
index 4074656..009dd2f 100644
--- a/yaksh/templates/user.html
+++ b/yaksh/templates/user.html
@@ -34,7 +34,7 @@
         <li><a href="{{ URL_ROOT }}/exam/changepassword">Change Password</a></li>
       </ul>
 	<ul style="float:right;">
-	<li><strong><a style='cursor:pointer' onClick='location.replace("{{URL_ROOT}}/exam/complete/");'>Log out</a></strong></li>
+	<li><strong><a style='cursor:pointer' onClick='location.replace("{{URL_ROOT}}/exam/complete/");' id='logout'>Log out</a></strong></li>
         </ul>
      </div>
    </div>
diff --git a/yaksh/templates/yaksh/addteacher.html b/yaksh/templates/yaksh/addteacher.html
index 7e04f71..6722a52 100644
--- a/yaksh/templates/yaksh/addteacher.html
+++ b/yaksh/templates/yaksh/addteacher.html
@@ -18,6 +18,7 @@
 		<button class="btn" type="button" name="button" onClick='location.replace("{{URL_ROOT}}/exam/manage/courses");'>Cancel</button> </center></form>
 </div>
 <br><br>
+
 <form action="{{ URL_ROOT }}/exam/manage/addteacher/{{ course.id }}/" method="post">
 {% csrf_token %}
 {% if success == True %}
@@ -56,8 +57,7 @@
 </form>
 {% if status == True %}
 <div class="row">
-    <div class="span6 offset4 wrap">
-        <center><b><u>Teacher(s) Added</u></b></center><br>
+    <div class="span6 offset4 wrap">  
         {% if teachers_added %}
         {% for teacher in teachers_added %}
         <div class="well">
diff --git a/yaksh/templates/yaksh/complete.html b/yaksh/templates/yaksh/complete.html
index 07cbf3a..98adf9b 100644
--- a/yaksh/templates/yaksh/complete.html
+++ b/yaksh/templates/yaksh/complete.html
@@ -29,5 +29,5 @@
 		<center><h2> Good bye! </h2></center>
 		<center><h4> {{message}} </h4></center>
 		<br><center><h4>You may now close the browser.</h4></center><br>
-	<center><a href="{{URL_ROOT}}/exam/"> Login Again </a></center>
+	<center><a href="{{URL_ROOT}}/exam/" id="login_again"> Login Again </a></center>
 {% endblock content %}
diff --git a/yaksh/templates/yaksh/courses.html b/yaksh/templates/yaksh/courses.html
index 06c848c..42f49d1 100644
--- a/yaksh/templates/yaksh/courses.html
+++ b/yaksh/templates/yaksh/courses.html
@@ -9,15 +9,12 @@
 {% endblock %}
 
 {% block manage %}
-<a href="{{URL_ROOT}}/exam/manage/allotted_course/">View Allotted Courses</a><br>
+
 {% if not courses %}
-    <center><h4> No new Courses added </h4></center>
+    <center><h4> No new Courses created </h4></center>
 {% else %}
-<center><h3> Course(s) Added</h3></center>
+<center><h3> Course(s) Created</h3></center>
     {% for course in courses %}
-    {% if user != course.creator %}
-        <h4> {{course.creator.get_full_name}} added you to this course</h4>
-    {% endif %}
     <div class="row show-grid">
         <div class="span14">
             <div class="row">
@@ -79,7 +76,76 @@
     </div>
     <br><br>
     {% endfor %}
-    <button class="btn primary" type="button" onClick='location.replace("{{URL_ROOT}}/exam/manage/add_course");'>Add New Course</button>
-    <button class="btn primary" type="button" onClick='location.replace("{{URL_ROOT}}/exam/manage/addquiz");'>Add New Quiz</button>
+    {% endif %}
+
+{% if allotted_courses %}
+    <center><h3> Course(s) Allotted </h3></center>
+
+    {% for course in allotted_courses %}
+        <div class="row show-grid">
+        <div class="span14">
+            <div class="row">
+                <div class="span6">
+                    <p>
+                        <b><u>Course</u></b>
+                        {% if course.active %}
+                            <span class="label success">Active</span>
+                        {% else %}
+                            <span class="label important">Closed</span>
+                        {% endif %}
+                    </p>
+                    <a href="{{URL_ROOT}}/exam/manage/course_detail/{{course.id}}/">{{ course.name }}</a>
+                    </br></br>
+                    <div class="row">
+                        <div class="span6 wrap">
+                            <center><b><u> Course Creator</u></b></center>
+                            {{course.creator}}
+                            <center><b><u>Teacher(s) Added to {{ course }}</u></b></center>
+                            {% if course.get_teachers %}
+                            <div align="left">
+                            <form action="{{URL_ROOT}}/exam/manage/remove_teachers/{{ course.id }}/" method="post">
+                            {% csrf_token %}
+                            {% for teacher in course.get_teachers %}
+                            <div class="well">
+                                <div class="row">
+                                    <div class="span3" style="width: auto;">
+                                        <input type="checkbox" name="remove" value="{{ teacher.id }}">&nbsp;{{ teacher.get_full_name }}
+                                    </div>
+                                </div>
+                            </div>
+                            {% endfor %}
+                            <button class="btn success" type="submit">Remove Selected</button>
+                            </div>
+                            {% else %}
+                            <center><b>No Teacher(s) Added</b></center>
+                            {% endif %}
+                            </form>
+                        </div>
+                    </div>
+                </div>
+                <div class="span6">
+                    <p><b><a href="{{URL_ROOT}}/exam/manage/searchteacher/{{course.id}}/">Add Teacher</a></b></p>
+                </div>
+                <div class="span6">
+                    <p><b><u>Quiz(zes)</u></b></p>
+                    {% if course.get_quizzes %}
+                        {% for quiz in course.get_quizzes %}
+                            <a href="{{URL_ROOT}}/exam/manage/addquiz/{{quiz.id}}/">{{ quiz.description }}</a><br>
+                    {% endfor %}
+                    {% else %}
+                        <p><b>No quiz </b></p>
+                    {% endif %}
+                </div>
+            </div>
+        </div>
+    </div>
+    <br><br>
+    {% endfor %}
+{% else %}
+    <center><h4> No new Courses allotted </h4></center>
 {% endif %}
+<button class="btn primary" type="button" onClick='location.replace("{{URL_ROOT}}/exam/manage/add_course");'>Add New Course</button>
+    {% if courses or allotted_courses %}
+    <button class="btn primary" type="button" onClick='location.replace("{{URL_ROOT}}/exam/manage/addquiz");'>Add New Quiz</button>
+{% endif %}    
 {% endblock %}
diff --git a/yaksh/templates/yaksh/question.html b/yaksh/templates/yaksh/question.html
index 2d52009..9a0f899 100644
--- a/yaksh/templates/yaksh/question.html
+++ b/yaksh/templates/yaksh/question.html
@@ -85,21 +85,6 @@ function call_skip(url)
     form.action = url
     form.submit();
 }
-    {% if error_message == 'Correct Output'%}
-	{% if paper.questions_left  %}
-	window.setTimeout(function()
-	{   
-		{% for qid in paper.questions.all  %}
-        location.href="{{ URL_ROOT }}/exam/{{ qid.id }}/check/{{ paper.attempt_number }}/{{ paper.question_paper.id }}/"
-		{% endfor %}		
-	}, 2000);
-	{% else %}
-	window.setTimeout(function()
-	{   
-		location.href="{{ URL_ROOT }}/exam/{{ question.id }}/check/{{ paper.attempt_number }}/{{ paper.question_paper.id }}/"
-	}, 2000);
-    {% endif %}
-	{% endif %}
 </script>
 
 {% endblock script %}
@@ -167,11 +152,17 @@ function call_skip(url)
          <input type=hidden name="question_id" id="question_id" value={{ question.id }}></input>
 
          {% if question.type == "mcq" %}
+        {% if error_message %}
+            <p>{{ error_message }}</p>
+        {% endif %}
          {% for test_case in test_cases %}
          <input name="answer" type="radio" value="{{ test_case.options }}" />{{ test_case.options }} <br/>
          {% endfor %}
          {% endif %}
          {% if question.type == "mcc" %}
+        {% if error_message %}
+            <p>{{ error_message }}</p>
+        {% endif %}
          {% for test_case in test_cases %}
          <input name="answer" type="checkbox" value="{{ test_case.options }}"> {{ test_case.options }}
          <br>
@@ -190,7 +181,7 @@ function call_skip(url)
 
          {% endif %}
  
-         {% if question.type == "mcq" or question.type == "mcc "%}
+         {% if question.type == "mcq" or question.type == "mcc"%}
          <br><button class="btn" type="submit" name="check" id="check">Submit Answer</button>&nbsp;&nbsp;
          {% elif question.type == "upload" %}
          <br><button class="btn" type="submit" name="check" id="check" onClick="return validate();">Upload</button>&nbsp;&nbsp;
diff --git a/yaksh/templates/yaksh/user_data.html b/yaksh/templates/yaksh/user_data.html
index 04544f9..2e7db50 100644
--- a/yaksh/templates/yaksh/user_data.html
+++ b/yaksh/templates/yaksh/user_data.html
@@ -56,11 +56,15 @@ User IP address: {{ paper.user_ip }}
 </p>
 <p>Student answer: {{ answers.0 }}</p>
 {% else %}{# non-mcq questions #}
-<pre> 
-{% for answer in answers %}################################################################################
+{% for answer in answers %}
+{% if not answer.skipped %}
+<pre>
+###############################################################################
 {{ answer.answer.strip }}
 # Autocheck: {{ answer.error }}
-{% endfor %}</pre>
+</pre>
+{% endif %}
+{% endfor %}
 {% endif %}
 {% with answers|last as answer %}
 <p><em>Marks: {{answer.marks}} </em> </p>
diff --git a/yaksh/tests.py b/yaksh/test_models.py
index 5b87fc1..4861fee 100644
--- a/yaksh/tests.py
+++ b/yaksh/test_models.py
@@ -424,7 +424,7 @@ class AnswerPaperTestCases(unittest.TestCase):
         self.answerpaper.save()
         # answers for the Answer Paper
         self.answer_right = Answer(question=Question.objects.get(id=1),
-            answer="Demo answer", 
+            answer="Demo answer",
             correct=True, marks=1
         )
         self.answer_wrong = Answer(question=Question.objects.get(id=2),
@@ -458,20 +458,85 @@ class AnswerPaperTestCases(unittest.TestCase):
         # Test completed_question() method of Answer Paper
         question = self.answerpaper.completed_question(1)
         self.assertEqual(self.answerpaper.questions_left(), 2)
-        # Test skip() method of Answer Paper
+
+        # Test next_question() method of Answer Paper
         current_question = self.answerpaper.current_question()
         self.assertEqual(current_question.id, 2)
-        next_question_id = self.answerpaper.skip(current_question.id)
+
+        # When
+        next_question_id = self.answerpaper.next_question(current_question.id)
+
+        # Then
         self.assertTrue(next_question_id is not None)
         self.assertEqual(next_question_id.id, 3)
+
+        # Given, here question is already answered
+        current_question_id = 1
+
+        # When
+        next_question_id = self.answerpaper.next_question(current_question_id)
+
+        # Then
+        self.assertTrue(next_question_id is not None)
+        self.assertEqual(next_question_id.id, 2)
+
+        # Given, wrong question id
+        current_question_id = 12
+
+        # When
+        next_question_id = self.answerpaper.next_question(current_question_id)
+
+        # Then
+        self.assertTrue(next_question_id is not None)
+        self.assertEqual(next_question_id.id, 2)
+
+        # Given, last question in the list
+        current_question_id = 3
+
+        # When
+        next_question_id = self.answerpaper.next_question(current_question_id)
+
+        # Then
+        self.assertTrue(next_question_id is not None)
+        self.assertEqual(next_question_id.id, 2)
+
+        # Test get_questions_answered() method
+        # When
         questions_answered = self.answerpaper.get_questions_answered()
+
+        # Then
         self.assertEqual(questions_answered.count(), 1)
         self.assertSequenceEqual(questions_answered, [self.questions[0]])
+
+        # When
         questions_unanswered = self.answerpaper.get_questions_unanswered()
+
+        # Then
         self.assertEqual(questions_unanswered.count(), 2)
         self.assertSequenceEqual(questions_unanswered,
                                  [self.questions[1], self.questions[2]])
 
+        # Test completed_question and next_question
+        # When all questions are answered
+        current_question = self.answerpaper.completed_question(2)
+
+        # Then
+        self.assertEqual(self.answerpaper.questions_left(), 1)
+        self.assertEqual(current_question.id, 3)
+
+        # When
+        current_question = self.answerpaper.completed_question(3)
+
+        # Then
+        self.assertEqual(self.answerpaper.questions_left(), 0)
+        self.assertTrue(current_question is None)
+
+        # When
+        next_question_id = self.answerpaper.next_question(current_question_id)
+
+        # Then
+        self.assertTrue(next_question_id is None)
+
     def test_update_marks(self):
         """ Test update_marks method of AnswerPaper"""
         self.answerpaper.update_marks('inprogress')
@@ -584,7 +649,7 @@ class CourseTestCases(unittest.TestCase):
     def test_add_teachers(self):
         """ Test to add teachers to a course"""
         self.course.add_teachers(self.student1, self.student2)
-        self.assertSequenceEqual(self.course.get_teachers(), 
+        self.assertSequenceEqual(self.course.get_teachers(),
                                      [self.student1, self.student2])
 
     def test_remove_teachers(self):
@@ -616,21 +681,21 @@ class CourseTestCases(unittest.TestCase):
 class TestCaseTestCases(unittest.TestCase):
     def setUp(self):
         self.user = User.objects.get(pk=1)
-        self.question1 = Question(summary='Demo question 1', 
+        self.question1 = Question(summary='Demo question 1',
             language='Python',
-            type='Code', 
+            type='Code',
             active=True,
-            description='Write a function', 
+            description='Write a function',
             points=1.0,
-            test_case_type="standardtestcase", 
+            test_case_type="standardtestcase",
             user=self.user,
             snippet='def myfunc()'
         )
-        self.question2 = Question(summary='Demo question 2', 
+        self.question2 = Question(summary='Demo question 2',
              language='Python',
-             type='Code', 
+             type='Code',
              active=True,
-             description='Write to standard output', 
+             description='Write to standard output',
              points=1.0,
              test_case_type="stdiobasedtestcase", 
              user=self.user,
@@ -658,13 +723,13 @@ class TestCaseTestCases(unittest.TestCase):
     def test_assertion_testcase(self):
         """ Test question """
         self.assertEqual(self.assertion_testcase.question, self.question1)
-        self.assertEqual(self.assertion_testcase.test_case, 
+        self.assertEqual(self.assertion_testcase.test_case,
                              'assert myfunc(12, 13) == 15')
 
     def test_stdout_based_testcase(self):
         """ Test question """
         self.assertEqual(self.stdout_based_testcase.question, self.question2)
-        self.assertEqual(self.stdout_based_testcase.expected_output, 
+        self.assertEqual(self.stdout_based_testcase.expected_output,
             'Hello World'
         )
 
diff --git a/yaksh/tests/__init__.py b/yaksh/tests/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/yaksh/tests/__init__.py
diff --git a/yaksh/tests/test_code_server.py b/yaksh/tests/test_code_server.py
new file mode 100644
index 0000000..a73f073
--- /dev/null
+++ b/yaksh/tests/test_code_server.py
@@ -0,0 +1,130 @@
+import json
+try:
+    from Queue import Queue
+except ImportError:
+    from queue import Queue
+from threading import Thread
+import unittest
+import urllib
+
+from yaksh.code_server import ServerPool, SERVER_POOL_PORT
+from yaksh import settings
+from yaksh.xmlrpc_clients import CodeServerProxy
+
+
+class TestCodeServer(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        settings.code_evaluators['python']['standardtestcase'] = \
+            "yaksh.python_assertion_evaluator.PythonAssertionEvaluator"
+        ports = range(8001, 8006)
+        server_pool = ServerPool(ports=ports, pool_port=SERVER_POOL_PORT)
+        cls.server_pool = server_pool
+        cls.server_thread = t = Thread(target=server_pool.run)
+        t.start()
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.server_pool.stop()
+        cls.server_thread.join()
+        settings.code_evaluators['python']['standardtestcase'] = \
+            "python_assertion_evaluator.PythonAssertionEvaluator"
+
+    def setUp(self):
+        self.code_server = CodeServerProxy()
+
+    def test_inifinite_loop(self):
+        # Given
+        testdata = {'user_answer': 'while True: pass',
+                    'test_case_data': [{'test_case':'assert 1==2'}]}
+
+        # When
+        result = self.code_server.run_code(
+            'python', 'standardtestcase', json.dumps(testdata), ''
+        )
+
+        # Then
+        data = json.loads(result)
+        self.assertFalse(data['success'])
+        self.assertTrue('infinite loop' in data['error'])
+
+    def test_correct_answer(self):
+        # Given
+        testdata = {'user_answer': 'def f(): return 1',
+                    'test_case_data': [{'test_case':'assert f() == 1'}]}
+
+        # When
+        result = self.code_server.run_code(
+            'python', 'standardtestcase', json.dumps(testdata), ''
+        )
+
+        # Then
+        data = json.loads(result)
+        self.assertTrue(data['success'])
+        self.assertEqual(data['error'], 'Correct answer')
+
+    def test_wrong_answer(self):
+        # Given
+        testdata = {'user_answer': 'def f(): return 1',
+                    'test_case_data': [{'test_case':'assert f() == 2'}]}
+
+        # When
+        result = self.code_server.run_code(
+            'python', 'standardtestcase', json.dumps(testdata), ''
+        )
+
+        # Then
+        data = json.loads(result)
+        self.assertFalse(data['success'])
+        self.assertTrue('AssertionError' in data['error'])
+
+    def test_multiple_simultaneous_hits(self):
+        # Given
+        results = Queue()
+
+        def run_code():
+            """Run an infinite loop."""
+            testdata = {'user_answer': 'while True: pass',
+                        'test_case_data': [{'test_case':'assert 1==2'}]}
+            result = self.code_server.run_code(
+                'python', 'standardtestcase', json.dumps(testdata), ''
+            )
+            results.put(json.loads(result))
+
+        N = 10
+        # When
+        import time
+        threads = []
+        for i in range(N):
+            t = Thread(target=run_code)
+            threads.append(t)
+            t.start()
+
+        for t in threads:
+            if t.isAlive():
+                t.join()
+
+        # Then
+        self.assertEqual(results.qsize(), N)
+        for i in range(N):
+            data = results.get()
+            self.assertFalse(data['success'])
+            self.assertTrue('infinite loop' in data['error'])
+
+    def test_server_pool_status(self):
+        # Given
+        url = "http://localhost:%s/status"%SERVER_POOL_PORT
+
+        # When
+        data = urllib.urlopen(url).read()
+
+        # Then
+        expect = 'out of 5 are free'
+        self.assertTrue(expect in data)
+        expect = 'Load:'
+        self.assertTrue(expect in data)
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/yaksh/urls.py b/yaksh/urls.py
index cd97dd4..d14ed1d 100644
--- a/yaksh/urls.py
+++ b/yaksh/urls.py
@@ -97,7 +97,6 @@ urlpatterns += [
         views.reject, {'was_enrolled': True}),
     url(r'^manage/searchteacher/(?P<course_id>\d+)/$', views.search_teacher),
     url(r'^manage/addteacher/(?P<course_id>\d+)/$', views.add_teacher, name='add_teacher'),
-    url(r'^manage/allotted_course/$', views.allotted_courses),
     url(r'^manage/remove_teachers/(?P<course_id>\d+)/$', views.remove_teachers, name='remove_teacher'),
     url(r'^manage/download_questions/$', views.show_all_questions),
     url(r'^manage/upload_questions/$', views.show_all_questions),
diff --git a/yaksh/views.py b/yaksh/views.py
index e1ec44e..923b3c2 100644
--- a/yaksh/views.py
+++ b/yaksh/views.py
@@ -454,16 +454,22 @@ def skip(request, q_id, next_q=None, attempt_num=None, questionpaper_id=None):
     paper = get_object_or_404(AnswerPaper, user=request.user, attempt_number=attempt_num,
             question_paper=questionpaper_id)
     question = get_object_or_404(Question, pk=q_id)
+    if question in paper.questions_answered.all():
+        next_q = paper.next_question(q_id)
+        return show_question(request, next_q, paper)
+
     if request.method == 'POST' and question.type == 'code':
         user_code = request.POST.get('answer')
         new_answer = Answer(question=question, answer=user_code,
                             correct=False, skipped=True)
         new_answer.save()
         paper.answers.add(new_answer)
-    if next_q is None:
-        next_q = paper.skip(q_id) if paper.skip(q_id) else question
-    else:
+    if next_q is not None:
         next_q = get_object_or_404(Question, pk=next_q)
+        if next_q not in paper.questions_unanswered.all():
+            return show_question(request, question,  paper)
+    else:
+        next_q = paper.next_question(q_id)
     return show_question(request, next_q, paper)
 
 
@@ -475,7 +481,7 @@ def check(request, q_id, attempt_num=None, questionpaper_id=None):
             question_paper=questionpaper_id)
     question = get_object_or_404(Question, pk=q_id)
     if question in paper.questions_answered.all():
-        next_q = paper.skip(q_id)
+        next_q = paper.next_question(q_id)
         return show_question(request, next_q, paper)
 
     if request.method == 'POST':
@@ -504,7 +510,9 @@ def check(request, q_id, attempt_num=None, questionpaper_id=None):
                             correct=False)
         new_answer.save()
         paper.answers.add(new_answer)
-
+        if not user_answer:
+            msg = "Please submit a valid option or code"
+            return show_question(request, question, paper, msg)
         # If we were not skipped, we were asked to check.  For any non-mcq
         # questions, we obtain the results via XML-RPC with the code executed
         # safely in a separate process (the code_server.py) running as nobody.
@@ -525,17 +533,8 @@ def check(request, q_id, attempt_num=None, questionpaper_id=None):
             new_answer.save()
             return show_question(request, question, paper, result.get('error'))
         else:
-            # Display the same question if user_answer is None
-            if not user_answer:
-                msg = "Please submit a valid option or code"
-                return show_question(request, question, paper, msg)
-            elif question.type == 'code' and user_answer:
-                msg = "Correct Output"
-                paper.completed_question(question.id)
-                return show_question(request, question, paper, msg)
-            else:
-                next_q = paper.completed_question(question.id)
-                return show_question(request, next_q, paper)
+            next_q = paper.completed_question(question.id)
+            return show_question(request, next_q, paper)
     else:
         return show_question(request, question, paper)
 
@@ -558,11 +557,13 @@ def validate_answer(user, user_answer, question, json_data=None):
             expected_answer = question.get_test_case(correct=True).options
             if user_answer.strip() == expected_answer.strip():
                 correct = True
+                result['error'] = 'Correct answer'
         elif question.type == 'mcc':
             expected_answers = []
             for opt in question.get_test_cases(correct=True):
                 expected_answers.append(opt.options)
             if set(user_answer) == set(expected_answers):
+                result['error'] = 'Correct answer'
                 correct = True
         elif question.type == 'code':
             user_dir = get_user_dir(user)
@@ -664,8 +665,10 @@ def courses(request):
     if not is_moderator(user):
         raise Http404('You are not allowed to view this page')
     courses = Course.objects.filter(creator=user, is_trial=False)
-    return my_render_to_response('yaksh/courses.html', {'courses': courses},
-                                context_instance=ci)
+    allotted_courses = Course.objects.filter(teachers=user, is_trial=False)
+    context = {'courses': courses, "allotted_courses": allotted_courses}
+    return my_render_to_response('yaksh/courses.html', context,
+                                 context_instance=ci)
 
 
 @login_required
@@ -1164,25 +1167,24 @@ def search_teacher(request, course_id):
         raise Http404('You are not allowed to view this page!')
 
     context = {}
-    course = get_object_or_404(Course, creator=user, pk=course_id)
+    course = get_object_or_404(Course, pk=course_id)
     context['course'] = course
 
+    if user != course.creator and user not in course.teachers.all():
+       raise Http404('You are not allowed to view this page!')
+
     if request.method == 'POST':
         u_name = request.POST.get('uname')
-        if len(u_name) == 0:
-            return my_render_to_response('yaksh/addteacher.html', context,
-                                        context_instance=ci)
-        else:
+        if not len(u_name) == 0:
             teachers = User.objects.filter(Q(username__icontains=u_name)|
                 Q(first_name__icontains=u_name)|Q(last_name__icontains=u_name)|
-                Q(email__icontains=u_name)).exclude(Q(id=user.id)|Q(is_superuser=1))
+                Q(email__icontains=u_name)).exclude(Q(id=user.id)|Q(is_superuser=1)|
+                                                    Q(id=course.creator.id))
             context['success'] = True
             context['teachers'] = teachers
-            return my_render_to_response('yaksh/addteacher.html', context,
-                                        context_instance=ci)
-    else:
-        return my_render_to_response('yaksh/addteacher.html', context,
-                                    context_instance=ci)
+                                        
+    return my_render_to_response('yaksh/addteacher.html', context,
+                                 context_instance=ci)
 
 
 @login_required
@@ -1196,8 +1198,11 @@ def add_teacher(request, course_id):
         raise Http404('You are not allowed to view this page!')
 
     context = {}
-    course = get_object_or_404(Course, creator=user, pk=course_id)
-    context['course'] = course
+    course = get_object_or_404(Course, pk=course_id)
+    if user == course.creator or user in course.teachers.all():
+        context['course'] = course
+    else:
+        raise Http404('You are not allowed to view this page!')
 
     if request.method == 'POST':
         teacher_ids = request.POST.getlist('check')
@@ -1206,25 +1211,10 @@ def add_teacher(request, course_id):
         course.add_teachers(*teachers)
         context['status'] = True
         context['teachers_added'] = teachers
-        return my_render_to_response('yaksh/addteacher.html', context,
+        
+    return my_render_to_response('yaksh/addteacher.html', context,
                                     context_instance=ci)
-    else:
-        return my_render_to_response('yaksh/addteacher.html', context,
-                                    context_instance=ci)
-
-
-@login_required
-def allotted_courses(request):
-    """  show courses allotted to a user """
 
-    user = request.user
-    ci = RequestContext(request)
-    if not is_moderator(user):
-        raise Http404('You are not allowed to view this page!')
-
-    courses = Course.objects.filter(teachers=user)
-    return my_render_to_response('yaksh/courses.html', {'courses': courses},
-                                        context_instance=ci)
 
 
 @login_required
@@ -1232,10 +1222,10 @@ def remove_teachers(request, course_id):
     """  remove user from a course """
  
     user = request.user
-    if not is_moderator(user):
+    course = get_object_or_404(Course, pk=course_id)
+    if not is_moderator(user) and (user != course.creator and user not in course.teachers.all()):
         raise Http404('You are not allowed to view this page!')
 
-    course = get_object_or_404(Course, creator=user, pk=course_id)
     if request.method == "POST":
         teacher_ids = request.POST.getlist('remove')
         teachers = User.objects.filter(id__in=teacher_ids)
diff --git a/yaksh/xmlrpc_clients.py b/yaksh/xmlrpc_clients.py
index 7124550..6bfe0d6 100644
--- a/yaksh/xmlrpc_clients.py
+++ b/yaksh/xmlrpc_clients.py
@@ -3,6 +3,7 @@ import time
 import random
 import socket
 import json
+import urllib
 
 from settings import SERVER_PORTS, SERVER_POOL_PORT
 
@@ -21,7 +22,7 @@ class CodeServerProxy(object):
     """
     def __init__(self):
         pool_url = 'http://localhost:%d' % (SERVER_POOL_PORT)
-        self.pool_server = ServerProxy(pool_url)
+        self.pool_url = pool_url
 
     def run_code(self, language, test_case_type, json_data, user_dir):
         """Tests given code (`answer`) with the `test_code` supplied.  If the
@@ -34,7 +35,7 @@ class CodeServerProxy(object):
         ----------
         json_data contains;
         user_answer : str
-            The user's answer for the question. 
+            The user's answer for the question.
         test_code : str
             The test code to check the user code with.
         language : str
@@ -57,21 +58,7 @@ class CodeServerProxy(object):
         return result
 
     def _get_server(self):
-        # Get a suitable server from our pool of servers.  This may block.  We
-        # try about 60 times, essentially waiting at most for about 30 seconds.
-        done, count = False, 60
-
-        while not done and count > 0:
-            try:
-                port = self.pool_server.get_server_port()
-            except socket.error:
-                # Wait a while try again.
-                time.sleep(random.random())
-                count -= 1
-            else:
-                done = True
-        if not done:
-            raise ConnectionError("Couldn't connect to a server!")
+        port = json.loads(urllib.urlopen(self.pool_url).read())
         proxy = ServerProxy('http://localhost:%d' % port)
         return proxy