Week 6

Week 6 - Scripting, CI, and Autograding

Lecture Materials

Bonus Lecture Videos

Extra Video Shorts

Skill Demo 1 Solution Video

Note: Links will require you to log in as a UCSD student

Lab Tasks

Discuss with your group:


Write down your answers (and why you chose them!) in your group’s shared doc.

In this week’s lab you will write an automatic “grader” for some of the methods we worked on in week 3.

In particular, you’ll write a script and a test file that gives a score to the functionality of a student-submitted ListExamples file and class (see ListExamples.java). The specific format is that you’ll write a bash script that takes the URL of a Github repository and prints out a grade:

$ bash grade.sh https://github.com/some-username/some-repo-name
... messages about points ...

This will work with a test file that you write in order to grade students’ work. You can use this repository to get started with your grader implementation; you should make a fork:


As part of your work, you’ll need to add new tests (or copy them from your work from lab 3) to the testing file, because the few tests that are there aren’t sufficient for grading. You can do that incrementally as you try out the script you write below on different student submissions.

Your Grading Script

Do the work below in pairs—as a pair, you should produce one implementation—push it to one member’s fork of the starter Github repository and include the link to that repository in your notes.

When your script gets a student submission it should produce either:

  • A grade message that says something about a score (maybe pass/fail, or maybe a proportion of tests passed – your choice) if the tests run.
  • A useful feedback message that says what went wrong if for any reason the tests couldn’t be run (compile error, wrong file submitted, etc.)

A general workflow for your script could be:

  1. Clone the repository of the student submission to a well-known directory name (provided in starter code) This is done by the git clone command in the provided script
  2. Check that the student code has the correct file submitted. If they didn’t, detect and give helpful feedback about it. This is not done by the provided code, you should figure out where to add it
  3. Get the student code, the .java file with the grading tests, and any other files the script needs into the grading-area directory. The grading-area directory is created for you, but you should move the files there.
    • Useful tools here might be cp (also look up the -r option to cp)
  4. Compile your tests and the student’s code from the appropriate directory with the appropriate classpath commands (remember that if you’re testing locally on Windows, the classpath is different). If the compilation fails, detect and give helpful feedback about it. You should add this
    • Aside from the necessary javac, useful tools here are output redirection and error codes ($?) along with if
    • This might be a time where you need to turn off set -e. Why?
  5. Run the tests and report the grade based on the JUnit output. You should add this
    • Again output redirection will be useful, and also tools like grep could be helpful here

Work incrementally – make sure you understand what the given code does. Then add steps incrementally. After each step, run on a test student submission and check for syntax errors, debug that step, add echo statements to check what’s stored in variables, and so on. Try running it more than once – is there any set up or cleanup you need to do before or after running it? Don’t write the whole thing. Refer to lecture from Monday to see some ways Joe did this incrementally in class.

Write down in notes screenshots of what your grader does on each of the sample student cases below.

“Student” Submissions

Assume the assignment spec was to submit:

  • A repository with a file called ListExamples.java
  • In that file, a class called ListExamples
  • In that class, two methods:
    • static List<String> filter(List<String> s, StringChecker sc)
    • static List<String> merge(List<String> list1, List<String> list2)
  • These methods should have the implementations suggested in lab 3

You should use the following repositories to test your grader:

Other Student Submissions

After you’re satisfied with the behavior on all of those submissions, write your own. Try to come up with at least two examples:

  • One that is wrong but is likely to get full scores
  • One that is mostly correct but crashes the grader and doesn’t give a nice error back (and is likely to cause a Piazza/EdStem post saying “the grader is broken!”)

You should create these as new, public Github repositories, so that you can run them using the same grader script by providing the Github URL.

Write down in notes: Run everyone’s newly-developed student submissions on everyone’s grader. That means each team should be running commands like

bash grade.sh <student-submission-from-some-group>

Whose grading script is the most user-friendly across those tests?

Running it Through a Server

We’ve also provided our Server.java and a server we wrote for you called GradeServer.java in the starter repository.

You can compile them and use

java GradeServer 4000

to run the server.

Look at the code to understand the expected path and parameters in GradeServer.java. Loading a URL at the /grade path with one of the repos above as the query parameter. What happens?

That’s quite a bit of the way towards an autograder like Gradescope!

Write down in notes: Show a screenshot of the server running your autograder in a browser.

Discuss and write down: What other features are needed to make this work more like Gradescope’s autograder? (Think about running for different students, storing grades, presenting results, etc)

Congratulations! You’ve done one kind of the work that your TAs do when setting up classes 🙂