TestSuite objects behave much like TestCase objects,
except they do not actually implement a test. Instead, they are used
to aggregate tests into groups that should be run together. Some
additional methods are available to add tests to TestSuite
instances:
Run the tests associated with this suite, collecting the result into
the test result object passed as result. Note that unlike
TestCase.run(), TestSuite.run() requires the
result object to be passed in.
In the typical usage of a TestSuite object, the run()
method is invoked by a TestRunner rather than by the end-user
test harness.