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C

Overview

An AutoTest V2 configuration for a C assignment has two stages:
  • The Setup stage: this is where you setup the auto grading environment. You can install packages and upload files. This builds into an image on which all tests are executed. All the configuration here only runs once for all submissions;
  • The Tests stage: this is what students will see and where you can configure all your tests that you want to run on every student’s code. Everything that you specify here is executed in the working directory of the student.
Steps are created in a “Scratch-like” block layout and can be dragged and dropped, reordered and nested to create an AutoTest program. We are continuously adding new blocks to AutoTest V2 to make it more powerful and easier to use.
AutoTest V2 is still available next to our original AutoTest, to start setting up an AutoTest V2 select AutoTest V2 when creating a new AutoTest. Already have an original AutoTest? You can switch to AutoTest V2 by deleting it and pressing "Select another version of AutoTest" to finally select AutoTest V2. Please note that your original AutoTest will be deleted when pressing the "Delete" button!

Developing, snapshots and publishing to students

When developing your AutoTest V2 configuration, you can continuously test your configuration on the "Test Submission".
After configuring something, you press the “Build Snapshot” button in the bottom right corner of the screen. This will Build your AutoTest into a Snapshot (a history of your snapshots are available via the Snapshots tab).
After pressing "Build Snapshot", you can:
  • Test the configuration by seeing the results in seconds.
  • If you are ready to publish your AutoTest to your students press the big green Publish button.
  • If you make any changes, you build again and if you are satisfied, you can republish them to your students.
  • If you want to unpublish your snapshot, you can simply go to it in the green bar and press the red “Unpublish” button.

Step 1: Setup

CodeGrade AutoTest V2 runs on Ubuntu (20.04 LTS) machines which you can configure in any way that you want. Common software is pre-installed, like make and gcc.
In the setup section of your AutoTest, you can install additional software or packages and upload any files you might need for testing. The setup section will build an image and is only run once for all submissions.
You can upload files using the "Upload Files" block, if you are intending on using Java Unit Testing using check for instance, this is where you will upload your unit test file. These files will be placed in the $UPLOADED_FILES directory on the Virtual Server.
You can install software and packages (or configure the build image in any other way) using the "Script" block. You have network access by default in the Setup tab, so you may also download libraries you want to use.
Optional setup for an autograded C assignment in AutoTest V2

Step 2: Create your tests

Now that you have created the setup, it's time to create the actual tests. This is done on the Tests tab. Select one of the many test-blocks to configure a AutoTest V2 procedure in a "scratch"-like format. Some tests can be nested and you can chose to connect tests to rubric categories with a certain weight, you can also hide aspects of tests and enable internet access for specific tests.

Set up an IO Test

IO Tests are great for console based programs and allow you to give an input to it and specify an expected output. The following will guide you to set up an IO Test:
A basic IO Test to check the output for a C program.
  1. 1.
    You will have to compile your students' C code somewhere. This may be in a "Script" block before your "IO Test" block. You may choose to compile the code using your preferred compiler, for the sake of this example we use gcc, we use: gcc -Wall fibonacci.c -o fibonacci.
  2. 2.
    Drag the "IO Test" block to your Test Procedure. In the code section, write the command to execute, for the compiled C code this could be something like ./fibonacci.
  3. 3.
    Drag one or more "Full Match" or "Substring Match" block(s) inside your "IO Test" block. Specify an Input (given via stdin / standard input) and an Expected Output.
  4. 4.
    Give clear names to the numerous blocks you have created to make clear to the students what is being tested.
  5. 5.
    Optionally: drag in a "Connect Rubric" block and drag your "IO Test" block in this, to connect it to a rubric category and use it to grade your students.

Set up a memory leak check (Valgrind)

Valgrind is a tool that can help detect memory leaks, see https://valgrind.org/ for more info. Valgrind is automatically installed on CodeGrade and can be used in a Run Program Test step to check for memory leaks:
  1. 1.
    Install valgrind in a "Script" block under the Setup tab using the commands:
    sudo apt update
    sudo apt install valgrind
  2. 2.
    Under the Tests tab, create a new Script block and run valgrind using the command: valgrind --leak-check=yes --error-exitcode=1 -q ./fibonacci. Replace ./fibonacci with your student's executable.
  3. 3.
    This will now pass if no memory leaks were found and fail otherwise!

Set up a Code Structure test

CodeGrade integrates a tool called Semgrep to make it easy to perform more complex code analysis by allowing you to write rules in a human readable format. You can provide generic or language specific patterns, which are then found in the code. With its pattern syntax, you can find:
  • Equivalences: Matching code that means the same thing even though it looks different.
  • Wildcards / ellipsis (...): Matching any statement, expression or variable.
  • Metavariables ($X): Matching unknown expressions that you do not yet know what they will exactly look like, but want to be the same variable in multiple parts of your pattern.

Writing the tests

Semgrep can be installed in the Setup step using pip, use: pip3 install semgrep. The easiest way to use Semgrep in AutoTest V2 is via our structure.py script (this will be built-in in a later version). With this script, you will write your Semgrep patterns directly in the Input field in an IO Test. Try out Semgrep patterns using their online editor here:
For instance, this is a ruleset to detect if a student uses the scanf function.
pattern: scanf(...);
We use the ellipses (the … in the pattern) here, so that any argument(s) can be given to scanf.

Creating the test in CodeGrade

structure.py
2KB
Text
Download the structure.py script to run Semgrep in AutoTest V2.
  1. 1.
    Under the Setup tab, upload the structure.py file you can download above. Also, in a "Script" block, install Semgrep via pip3 install semgrep.
  2. 2.
    Continue in the Tests tab: first drag the "IO Test" block to your Test Procedure. Execute the script in the code field, follow: python3 $UPLOADED_FILES/structure.py <STUDENTFILE>. For a Fibonacci assignment, this could be: python3 $UPLOADED_FILES/structure.py fibonacci.c.
  3. 3.
    Create and drag one or more "Simple Test" block(s) inside your "IO Test" block. Each block is one Semgrep structure to check. As Input write the Semgrep pattern (including pattern: or similar like pattern-either:).
  4. 4.
    As Expected Output write "Found!" if the student code should match or "Not found!" if the student code should not contain the pattern.
  5. 5.
    Optionally: Use a "Connect Rubric" block to connect your structure check to a rubric category.
  6. 6.
    Optionally: Use a "Hide" block to hide the "config" (i.e. input / pattern) of your tests so that students cannot see the pattern you are checking for.
A Semgrep structure check in an IO Test in AutoTest V2 (with optional Hide block to hide the pattern).
CodeGrade's AutoTest V2 supports many more types of tests, from linters to unit testing to custom test scripts. Further more, you can use specific blocks to hide, weight and grade tests. Want to set up a more advanced C autograder? Reach out to us via [email protected].

Step 3: Start the AutoTest

Once you have created a configuration, press start and your AutoTest will start running. In the General Settings, you should have already uploaded a Test Submission, so you will see the results of this straight away.
Once it's started and your assignment is set to Open or Done, students can hand in and get immediate feedback!