TestFixtures is a collection of helpers and mock objects that are
useful when writing unit tests or doc tests.
If you're wondering why "yet another mock object library", testing is
often described as an art form and as such some styles of library will
suit some people while others will suit other styles. This library
contains common test fixtures the author found himself
repeating from package to package and so decided to extract them into
their own library and give them some tests of their own!