Software Carpentry Day 8: Testing

Morning

The Nanotech example from last week doesn't include any error checking.

1. Make up half a dozen badly-formatted input files to share with other students. Try to make some of the flaws in your files very subtle.
2. Add error handling to your copy of Nanotech. How useful can you make the error messages? How many of the errors in your fellow students' files did you fail to catch?
3. The sample solution to Nanotech doesn't contain any comments. How annoying is this? What kind of comments would actually have been useful to remind you how the program works?

Afternoon

1. Using unittest, write some tests for the functions in the Nanotech example. If you want, you may modify the functions (e.g., replace filenames with CStringIO objects) in order to make things more testable.
2. Add three or four bugs (the subtler the better) to your copy of Nanotech and swap code with another team. How many of your bugs are their tests able to find? How many of theirs errors did yours find?
3. Bhargan Bitdiddle wants to know the cost of molecules. At NanoCore each atom costs its atomic number in cents. Write tests for a function that receives a molecule and returns its cost in cents. Then write the function, making each test pass in turn. Did your tests cover independent aspects of the functionality? Are there tests that always pass and fail together? Is there any part of the function left untested? What happens if a molecule is empty or contains invalid atoms?