Train the Test Driven Detective in Test Driven Deduction using Test Driven Development.
Run the tests, you'll find several cases set out already, but the detective can't solve() them!
Add solve() to the detective, you should be able to solve the first three cases without touching any other file.
Add a Witness class to help the detective out, the Witness should be able to take a list of arguments to describe what they saw.
This task will require you to refactor more than just the detective, you may even need to refactor the tests.
Make the crimes tougher, the detective smarter.
Add your own unique twist.