'Verify that setting the variable to a certain value returns
the expected boolean for it.
As environment variables are only stored as strings, we have to cast
whatever it\'s set at to a boolean that does not violate expectations.'

def check_val(self, set_val, expected_val):

    _orig_environ = dict(os.environ)
    os.environ['NO_PREREQ_INSTALL'] = set_val
    self.assertEqual(no_prereq_install(), expected_val, 'NO_PREREQ_INSTALL    is    set    to    {},    but    we    read    it    as    {}'.format(set_val, expected_val))
    os.environ.clear()
    os.environ.update(_orig_environ)
