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Homework 5

Due Friday Mar 15th at 4:00pm EST

In this homework, you will use Hypothesis, a property-based testing tool, to find an obscure-ish bug in Wordle.

Please read the entire assignment in full before you begin. You might find some helpful information in the Resources section.

Learning goals

  • Think of a property that should always hold for function is_yellow.
  • Describe the property in your own words
  • Use Hypothesis to implement your property test for is_yellow
  • Find an obscure Wordle bug using Hypothesis


For this assignment, you will test a buggy version of Wordle using Hypothesis and try to find a bug.

You will perform the following tasks. You can use Codespaces for this assignment.

  • Install Hypothesis
  • Setup your hw5 folder
  • Define your is_yellow property in your own words
  • Implement your property in
  • Find the bug using Hypothesis
  • Bonus Challenge: Fix the bug!

Install Hypothesis

Using the terminal in your homework repo:

pip install hypothesis

Setup your hw5 folder

  1. In your homework repo:
    mkdir hw5
    cd hw5
  2. Dowload the following files into hw5:
  3. Create a blank in hw5
  4. Stage, commit, and push to the remote repository

Define your is_yellow property in your own words

Think about the cases when is_yellow should return true and when it should return false. Without re-implementing is_yellow can you think of some ways to predict when is_yellow might return true and when it might return false?

This may take some time and creativity. Write the property you choose in your own words in

Implement your property in

Write a short test in function test_is_yellow_pbt that you think might find the bug.

Note: Short here means under 10 lines of code; if writing more than that you may want to consider a simpler property.

Find the bug using Hypothesis

To execute Hypothesis, run pytest in terminal with hw5 as your current working directory.

If all tests pass, Hypothesis will say the tests passed (meaning it didn’t find the bug). If a test fails, Hypothesis will show you a single example as well as the assertion that failed. The documentation (see Resources) also explains this.

When you find the bug, update with:

  • The counter-example Hypothesis found
  • Describe your experience trying to find the bug. Do you think this might be harder or easier than manually thinking of test cases?
  • Is there anything that you liked or disliked about using Hypothesis? How do you think it could be better or easier to use?

Note: If your property didn’t find a bug, you should consider other properties to test.

Bonus Challenge: Fix the Bug!

Correct the bug: include a corrected version of Wordle in your repo named


Tips and Suggestions

You can assume that is_green and is_red are correctly implemented. If you get completely stuck, consider whether any position may ever be anything other than red, green, or yellow.

Deadlines and Deliverables

Due Date: Friday March 15th at 4:00pm EST

The deliverable should be committed and pushed to the main branch of your repository on GitHub inside a hw5 subdirectory.