Creating assignments

In this chapter you will learn how to create an assignment. We will create a simple Python application with a single function add(a: int, b: int).

This chapter covers the following:

  • How to create an assignment and tasks

  • How to provide a basic file boilerplate to your students

  • How to define evaluations for your tasks

  • Running your tests locally

1. Prepare your tasks

Preparation is key! Don’t start working with Code FREAK if you haven’t thought about what to test and how to test. Before you start adding Code FREAK configuration to your tasks, make sure they are working/compiling locally on your machine! You can also test execution like Code FREAK does locally by installing Docker. More on this in section Testing locally with Docker.

Code FREAK allows students to write and execute their code without leaving the browser. Currently, we are using a browser-port of Microsoft’s VSCode by Coder. We recommend you also use VSCode for creating your tasks locally.

2. Creating the student boilerplate code

For this tutorial we use the following Python file with a single function add(a: int, b:int) → int. You can either let your student create these file or at least provide some initial template (boilerplate) to give them a fair starting point.
def add(a: int, b: int) -> int:
    # TODO: write the algorithm to add a and b
    return 0 (1)

if __name__ == "__main__":
    print("2 + 3 = %s" % add(2, 3))
1 This is the line the student has to correct to finish this task.

3. Writing tests

Which form of testing you choose for your tasks heavily depends on the tasks requirements. If students have to work on algorithms you should use some form of unit or functional testing. If they create a simple I/O application you can use a library that tests input and output.

In this example we will use pytest, a testing framework for Python. It is important that your testing framework supports jUnit XML output so Code FREAK is able to parse the results.

Alongside the file we will create a file that will contain some assertions to verify the add function.
from main import add

def test_function():
    assert add(2, 3) == 5
    assert add(-1, 2) == 1

You should verify that this works as expected on you local computer before continuing. We run the tests by executing the following command in the terminal.


This should give some output about a failing test. It is important that your tests are failing. Otherwise you could not expect your students to fix the faulty source code.

Failing pytest output
==================== test session starts =====================
platform linux -- Python 3.8.2, pytest-5.4.1, py-1.8.1, pluggy-0.13.1
rootdir: /home/user/python-example
collected 1 item F                                         [100%]

========================== FAILURES ==========================
_______________________ test_function ________________________

    def test_function():
>       assert add(2, 3) == 5
E       assert 0 == 5
E        +  where 0 = add(2, 3) AssertionError
================== short test summary info ===================
FAILED - assert 0 == 5
===================== 1 failed in 0.04s ======================

4. Creating the basic directory layout

You should already have a file and a file. Transform your directory layout to match the following.

/ (1)
├─ codefreak.yml (2)
├─ task-1/ (3)
│  ├─ codefreak.yml (4)
│  ├─ (5)
│  ├─ (6)
1 The / directory is the root of your assignment.
2 The codefreak.yml directory in your project contains the definition of the assignment. See Assignment’s codefreak.yml for further explanation on its contents.
3 The task-1 directory is the root directory of your Task. You can create as many tasks per project as you like. For this example we only have one task in our assignment.
4 The task-level codefreak.yml contains the configuration of your task, how it is evaluated, etc. See Task’s codefreak.yml for more information on its contents.
5 The is an example of boilerplate code you give to your students. You can also create tasks without any boilerplate code at all if you want your students to create everything on their on.
6 The file contains the tests we will run on our students code. Even if it is visible now we will hide it from students by using the task’s codefreak.yml.

5. Add Code FREAK configuration

We now have to add two configuration files to the directory-layout, so Code FREAK knows how to evaluate the task. As explained in the previous section there are two different codefreak.yml files: One for your assignment and one for each task.

Please see the Definition Files Chapter for a full reference of the codefreak.yml files.

5.1. Assignment’s codefreak.yml

Don’t worry you have never worked with YAML (.yml) files. The syntax is pretty straight forward and easy to read.
title: "Python assignment"
  - task-1

The codefreak.yml in your assignment root-directory is very slim. It only contains the title of your assignment and a list of directories that contain the individual tasks.

5.2. Task’s codefreak.yml

The codefreak.yml file in your task directory is where the magic happens. We will define two evaluation steps for our task: A static code analysis with Code Climate (because the config is super easy) and a unit test with pytest.

title: Create an addition function in Python (1)
description: |
   Please create an `add(a: int, b: int): int` function in the
  `` file, that returns the sum of parameter `a` and `b`.

   Find some useful help in the [official reference](
hidden: (2)
  - step: codeclimate (3)
  - step: junit (4)
      image: "python:3.7" (5)
      project-path: /code (6)
      results-path: . (7)
        - pip install pytest (8)
        - pytest --junitxml=TEST-report.xml (9)
1 The first two lines will add a title and some description to our task. The weird description syntax is a multi line string in YAML. The description allows basic Markdown syntax.
2 In the hidden property we define a list of directories and/or files that will be hidden from our students. Each instruction is a glob pattern. The codefreak.yml file is ALWAYS hidden for students.
3 The first evaluation step is Code Climate. If you don’t add any more options it will perform a basic static code analysis.
4 The second evaluation step is the actual unit testing. See the definition docs for a full reference of available options.
5 We use the official Python 3.7 Docker image for running the tests. This makes Code FREAK so flexible and allows you to use the Docker Image of your favorite programming language.
6 The project-path is the working directory inside your container. All commands will be executed relative to this path. This can be any directory.
7 The results-path is a path that will contain the jUnit XML files. Code FREAK will look for .xml files starting with TEST-*. The path is relative to the project-path!
8 Because the Docker container does not ship with pytest we have to install it first.
9 This is our actual pytest command that runs the test in our file and generates a TEST-report.xml file for Code FREAK.

You can already run the tests locally to check if they behave as expected by invoking the test command pytest --junitxml=TEST-report.xml

6. (optionally) Add VSCode configuration files

Students can use Code FREAK to program in their browsers. The programming environment is currently based on VSCode. We recommend that you add debugging configuration for VSCode, so your students can execute their source code in the browser. Please follow the official documentation on how to creating debugging/run configurations in VSCode.

The result should be a .vscode directory with a launch.json file. Add this directory to you task-1 directory.

7. Testing locally with Docker

Before you upload your assignment to Code FREAK you should try to run the tests locally with Docker. After installing Docker you can use the following command-template to test execution locally:

docker run -it --rm \
       -w <project-path> \
       -v $PWD:<project-path> \
       <image> \
       sh -c '<command #1> && <command #2> && <command #3> && ...'

The <variables> should be replaced by the corresponding values from your task’s codefreak.yml.

If you are on Windows replace the $PWD variable with the absolute path to your task-1 directory. On Mac OS and Linux the $PWD variable will be replaced accordingly.

This is an example for our task-1. Execute the following command in the task-1 directory:

docker run -it --rm \
       -w /code \
       -v $PWD:/code \
       python:3.7 \
       sh -c 'pip install pytest && pytest --junitxml=TEST-report.xml'

8. Creating and uploading an assignment

If your assignment is ready to be uploaded to Code FREAK you have to create a zip or tar archive. The archive name itself does not have to follow any naming scheme.

The root directory of the archive has to contain the assignment codefreak.yml file! So do not create a archive that contains another assignment-123 directory. Be warned that many archive programs do this by default. The safest way is selecting the codefreak.yml file and all task-* directory and use your context menu to create an archive of these file.


├─ codefreak.yml
├─ task-1/
│  ├─ codefreak.yml
│  ├─
│  ├─


├─ my-assignment/
│  ├─ codefreak.yml
│  ├─ task-1/
│  │  ├─ codefreak.yml
│  │  ├─
│  │  ├─
Code FREAK executes all commands on Linux. There might be cases where the file permissions are important. Either use a tar archive to retain file permissions or set the correct permissions in one of your commands.

After you created your archive go to your Code FREAK installation and create a new assignment by uploading the archive.