gistfile1.py

# test_my_module.py
import unittest

class MyClassTest(unittest.TestCase):
	
	def setUp(self):
		self.user = SomeUserClass()
		self.obj = MyClass(user=user)
		
	def test_valid_input(self):
		for i in xrange(18, 100):
			self.assertEqual(
				self.obj.handle_input(i),
				MyClass.STATUSES.OK
			)
		
	def test_invalid_input(self):
		for i in xrange(0, 17):
			self.assertEqual(
				self.obj.handle_input(i),
				MyClass.STATUSES.FAILED
			)
	
	def test_exception(self):
		with self.assertRaises(MyClass.InputException):
			self.obj.handle_input('xyz')
	
	def test_none_input(self):
		with self.assertRaises(MyClass.InputException):
			self.obj.handle_input(None)
	
	
# my_module.py
from myhelpermodule import Choices

class MyClass(object):

	class InputException(Exception):
		pass

	STATUSES = Choices(
		'OK',
		'FAILED',
		'NA',
	) 
	
	def __init__(self, user):
		self.user = user
		self.status = MyClass.STATUSES.NA
		
	def handle_input(self, n_in=None):
		if isinstance(n_in, int):
			if n_in >= 18 < 100:
				return MyClass.STATUSES.OK
			else:
				return MyClass.STATUSES.FAILED
		raise MyClass.InputException