nosedive is a plugin for the popular Nose unit test framework and runner for Python. nosedive aims to complement code coverage metrics by exposing how directly the code in the product under test is called from your unit tests.

I have found that code coverage metrics can be very misleading. Code coverage tools, such as Ned Batchelder's excellent coverage Nose plugin, give developers an incentive to increase their code's overall coverage index. In other words, I am encouraged to ensure that my unit tests cause 100% of the Python statements in the code under test to be executed. This doesn't necessarily mean that 100% of the statements in the code under test will be executed as part of a specific and meaningful unit test!

Enter nosedive. Whereas coverage reports how many of the statements in the code under test have been executed, nosedive reports the shortest call stack distance between your unit tests and every callable in the code under test that is called at least once. If for instance nosedive reports that product.widgets.foo.FooWidget.widgetise() has a score of 3, this means that the widgetise method defined on my FooWidget class in module product.widgets.foo is indeed reached by my unit tests, but only very indirectly. It is exercised most directly when it is called by something called by another something called by my unit test. This isn't necessarily wrong, but it may be a meaningful signal that I need to write more specific and focused unit tests for FooWidget.

nosedive does not require any dependency beside Python and Nose. To install, simply type:

pip install nosedive

You can also clone this repository and run the following from your working copy:

python setup.py install

Simply run

nosetests (other nose options) --with-nosedive

nosedive currently conflicts with the coverage Nose plugins. It is recommended that you do not run nose with both plugins enabled at the same time.

nosedive isn't very mature and does not have special handling for decorators. Therefore, decorated calls will be given a score that reflects the presence of the decorators in the call stack.