Doppelganger
Goal: learn about the various types of test doubles
Instructions
There are bugs in the code (marked with a Bug! comment), but all the
tests are passing.
For each test, you will find a TODO comment. Your job
is to implement a test double for each test, and to use it
to make the test fail for the right reason, i.e, triggering
the bugs. You must do so by adding only test code - you
are not allowed to change the production code.
Here's the order in which you should fix the test - they go from easiest to trickiest :)
- SafeCalculator
- DiscountApplier
- MailSender
Step 1 - without any library
For this step, you are not allowed to add any external library.
Make a commit when you're done fixing all the TODOs
Step 2 - with a library
Use a library like mockito for Java, unittest.mock for Python or
sinon for JavaScript to rewrite all the tests.
Make a second commit so you can compare test code with step 1.
Which version do you prefer?