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CodeRunner Documentation (V2.4.2)

1 Introduction

NOTE: This is the documentation for Version 2.4.2. Version 3.0.0 is now available and is documented here.

CodeRunner is a Moodle question type that requests students to submit program code to some given specification. The submission is graded by running a series of tests on the code in a sandbox, comparing the output with the expected output. A trivial example might be a Python function sqr(x) that returns its parameter squared, but there is essentially no limit on the complexity of questions that can be asked.

CodeRunner is intended to be run in an adaptive mode, so that students know immediately if their code is passing the tests. In the typical 'all-or-nothing' mode, all test cases must pass if the submission is to be awarded any marks. The mark for a set of questions in a quiz is then determined primarily by which questions the student is able to solve successfully and then secondarily by how many submissions the student makes on each question. However, it is also possible to run CodeRunner questions in a traditional quiz mode where the mark is determined by how many of the tests the code successfully passes.

CodeRunner and its predecessors pycode and ccode has been in use at the University of Canterbury for about five years, running many hundreds of thousands of student quiz submissions in Python, C , Octave and Matlab. Laboratory work, assignment work and mid-semester tests in the introductory first year Python programming course (COSC121), which has around 400 students in the first semester and 200 in the second, are all assessed using CodeRunner questions. The final exams for COSC121 have also been run using Moodle/CodeRunner since November 2014.

The second year C course (ENCE260) of around 200 students makes similar use of CodeRunner using C questions and a third year Civil Engineering course (ENCN305), taught in Matlab, uses CodeRunner for all labs and for the mid-semester programming exam. Other courses using Moodle/CodeRunner include:

  1. EMTH171 Mathematical Modelling and Computation
  2. COSC261 Formal Languages and Compilers
  3. COSC367 Computational Intelligence
  4. ENCE360 Operating Systems
  5. SENG365 Web Computing Architectures

CodeRunner currently supports Python2 (considered obsolescent), Python3, C, Java, PHP5, JavaScript (NodeJS), Octave and Matlab. C++ questions are not built-in but can be easily supported by custom question types. The architecture allows easy extension to other languages.

For security and load reasons, it is recommended that CodeRunner be set up on a special quiz-server rather than on an institution-wide Moodle server. However, CodeRunner does allow use of a remote sandbox machine for running all student-submitted code so provided only that sandbox is enabled, as discussed below, this version should actually be safe to install on an institutional server.

A single 4-core server can handle an average quiz question submission rate of about 60 quiz questions per minute while maintaining a response time of less than about 3 - 4 seconds, assuming the student code itself runs in a fraction of a second. We have run CodeRunner-based exams with around 250 students and experienced only light to moderate load factors on an 8-core Moodle server. The Jobe server, which runs student submissions (see below), is even more lightly loaded during such an exam.

The CodeRunner question type can be installed on any modern Moodle system (version 2.6 or later), on Linux, Windows and Mac. For security reasons submitted jobs are usually run on a separate machine called the "Jobe server" or "Jobe sandbox machine". Linux installations have the additional option of using the third-party Liu sandbox for running C jobs directly on the Moodle server and there is also a sandbox called the RunGuard sandbox built into CodeRunner, although the latter is now deprecated. See the Sandbox Configuration section for details. Note that the Jobe sandbox runs only on Linux systems.