TestCase

A class whose instances are single test cases.

By default, the test code itself should be placed in a method named
'runTest'.

If the fixture may be used for many test cases, create as
many test methods as are needed. When instantiating such a TestCase
subclass, specify in the constructor arguments the name of the test method
that the instance is to execute.

Test authors should subclass TestCase for their own tests. Construction
and deconstruction of the test's environment ('fixture') can be
implemented by overriding the 'setUp' and 'tearDown' methods respectively.

If it is necessary to override the __init__ method, the base class
__init__ method must always be called. It is important that subclasses
should not change the signature of their __init__ method, since instances
of the classes are instantiated automatically by parts of the framework
in order to be run.

When subclassing TestCase, you can set these attributes:
* failureException: determines which exception will be raised when
    the instance's assertion methods fail; test methods raising this
    exception will be deemed to have 'failed' rather than 'errored'.
* longMessage: determines whether long messages (including repr of
    objects used in assert methods) will be printed on failure in *addition*
    to any explicit message passed.
* maxDiff: sets the maximum length of a diff in failure messages
    by assert methods using difflib. It is looked up as an instance
    attribute so can be configured by individual tests if required.