def times_2_plus_1(arg1):
    result = _expensive_x2(arg1) + 1
    return result

import time

def _expensive_x2(arg1):
    time.sleep(3)  # expensive math, IO, 3rd-party API, etc.
    return arg1 * 2

times_2_plus_1(7)

import unittest


class TestMath(unittest.TestCase):
    
    def test_math(self):
        self.assertEquals(15, times_2_plus_1(7))
        
        
suite = unittest.TestLoader().loadTestsFromTestCase(TestMath)
unittest.TextTestRunner(verbosity=2).run(suite)
        



import unittest
import mock


class TestMath2(unittest.TestCase):
    
    @mock.patch('__main__._expensive_x2', mock.Mock(return_value=14))
    def test_math(self):
        self.assertEquals(15, times_2_plus_1(7))
        
        
suite = unittest.TestLoader().loadTestsFromTestCase(TestMath2)
unittest.TextTestRunner(verbosity=2).run(suite)

import unittest
import mock
import os

ENV = 'TEST_INTEGRATION'
REASON = "'{0}' not set".format(ENV)


class TestMath3(unittest.TestCase):
    
    @mock.patch('__main__._expensive_x2', mock.Mock(return_value=14))
    def test_math(self):
        self.assertEquals(15, times_2_plus_1(7))
        
    @unittest.skipUnless(os.getenv(ENV), REASON)
    def test_math_integration(self):
        self.assertEquals(15, times_2_plus_1(7))
        
        
suite = unittest.TestLoader().loadTestsFromTestCase(TestMath3)
results = unittest.TextTestRunner(verbosity=2).run(suite)
print results
print results.skipped

import os
os.environ['TEST_INTEGRATION'] = ''

import os
os.environ['TEST_INTEGRATION'] = '1'