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19 January 2014

GitHub + University: How College Coding Assignments Should Work

You can find the follow up post here as well as source code: GitHub + Univeristy: A Follow Up

This semester (Spring 2014), I’m a Teaching Assistant (TA) for a course that I took last semester called “Principles of Programming Languages.” It was a very enjoyable class and I have always been interested in programming languages. I felt that being a TA would be a great way to explore the learning process and subject matter more deeply.

An Idea

Through out my entire college career, all programming assignments have had to be submitted through BlackBoard. To be as diplomatic as possible, BlackBoard does a lot of things to help students & teachers. Unfortunately it does not do a single one of them well.

The normal way to submit coding assignments is to have homework assigned through BlackBoard and to have to code up the solutions and then zip them up and submit them using the web interface.

BlackBoard Issues

There are many different issues with this.

The first and most obvious is that it is tedious for each party (TA & the student) to zip and extract code. It can’t be automated (painlessly). BlackBoard has a series of iframes that make it incredibly hard to automate submission or retrieval of homework. Code should not be stored in zip files anymore. Distributing code is a solved problem by using version control systems.

GitHub to the Rescue

Lorand, one of the other TA’s, and I both came to the conclusion that using GitHub would be an interesting experiment. We were both very experienced with using Git as well as GitHub so we wanted to brainstorm how we could get a class of considerable size to do this.

The great part is that GitHub provides plenty of opportunities for students and teachers to get free access to normally pay-only features though the GitHub Education section.

Using this, the professor reached out to GitHub and was able to setup an Organization with 125 private repositories for free.

After typing up a little README with the course info, a guide to using Git + GitHub, as well as shamelessly stealing the Half-Life logo, we had an organization that was ready for the semester: ComS342-ISU.

Setting It Up

The first obstacle was that we wanted each student to have a private repository that would contain all their solutions in individual folders. We wanted the repositories to be only visible to the student it belonged to as well as the TA’s and instructor.

I knew that I would never want to individually create 50+ repositories and setup the correct push/pull access so I turned to GitHub’s API + NodeJS.

Automating Using the API

It only took a few hours but within short time I had a very simple web application that would allow the student to connect using their GitHub account through GitHub’s OAuth.

The application would then ask for their University login, check that they are actually registered for the class, and then automagically create a new private repository for them in the form hw-answers-<id> and add them to the Students team.

In addition to the creating of the repositories, I also made a script to check to see what students aren’t in the class that are currently registered and to automatically remind them that they need to register as soon as possible.

Source Code

After the class is finished, I’ll make the code to this little bot available on my GitHub.

How We Are Using the Repos

We have a few different repositories that we are using. The first repo is the only public one and it is the course-info repo. It contains the syllabus information as well as some basic guides to help the students set everything up.

The second repository is private but available for all the students to see. This is where we will release homeworks and publish solutions as they become available. This is also the repository that students are encouraged to discuss within the repositories Issue Tracker. This is replacing the discussion boards of the past.

The bulk of our repository usage (roughly 50) is each student’s repository to contain their answer sheets. These are essentially manual Forks of the main homework repository from the previous paragraph. The students are responsible for syncing their repositories with the official homework repository to bring in new homeworks as they are released.

There are a few other repositories like one for the code that I’ve created for the course and the grading infrastructure the other TA has created. We also have an internal homework repository that we use to organize all the future homeworks and to collaborate.

Grading & Feedback

The best part about using GitHub for homework submissions is that it is incredibly easy to give feedback and help the students through learning the material.

In the past, most feedback/grading is provided back to the student in a little .txt file that contains a few comments and the final grade.

With GitHub, we can comment on specific commits, specific lines of code, and see how the student progressed through the homework.

It is far more valuable to the student for this kind of interaction. Without using GitHub, it would be a lot more difficult because of the time it would require to do this.

When it comes to grading, all of our homeworks come with a suite of unit tests that test nearly every part of the homework. The students can get immediate feedback on how well they are doing.

This also makes it incredibly easy to grade. The other TA has created a bot written in Scala that grabs all of the homework repositories and runs the set of unit tests. The results are then written to a text file and pushed back to the repository.

We the TAs then can see the final status of their tests and then spend the rest of the time looking at the code to see why any of the tests failed and how they can improve their code.

This cuts out so much time that would be spent downloading zip files, extracting them, manually running the tests and so on.

Ways to Improve

So far only a week has passed since the semester started so there are a lot of unforeseen things that might happen. I’m sure I will think of other ways to improve this little system but there are a few major ones that I can see right now:

Continuous integration would be nice. Like I mentioned, we have to instruct the bot to grab the homeworks and test them. It would be great to use something like TravisCI to test every commit as it is pushed. The problem is that the homeworks need to be private but TravisCI is only free for open source projects. It would be great if TravisCI provided an Educational discount like GitHub. A more formal submission process. Right now we are saying that the code just needs to be pushed by the homework deadline. There is nothing that needs to be done to actually “submit” their homework. There are a few issues with this because if a student forges a commit time stamp, they can set the date a to be before the deadline and still push the code. We are looking into ways to counter this in the short term. The first that comes to my mind is to just run a bot shortly after the deadline to grab the SHA-1 HEAD of the master branch and its parent commits for every student’s repository. This would ensure that any tampering with the git log would be noticeable and change the SHA-1s.

Going Forward

Once the semester is finished, I will revisit the topic to see how things turned out. I really hope that things go well \^_\^.