Python test cheatsheet

A simple Python unittest

# python unittests only run the function with prefix "test"

>>> from __future__ import print_function
>>> import unittest
>>> class TestFoo(unittest.TestCase):
...     def test_foo(self):
...             self.assertTrue(True)
...     def fun_not_run(self):
...             print("no run")
...
>>> unittest.main()
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
>>> import unittest
>>> class TestFail(unittest.TestCase):
...     def test_false(self):
...             self.assertTrue(False)
...
>>> unittest.main()
F
======================================================================
FAIL: test_false (__main__.TestFail)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "<stdin>", line 3, in test_false
AssertionError: False is not true

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (failures=1)

Python unittest setup & teardown hierarchy

from __future__ import print_function

import unittest

def fib(n):
    return 1 if n<=2 else fib(n-1)+fib(n-2)

def setUpModule():
        print("setup module")
def tearDownModule():
        print("teardown module")

class TestFib(unittest.TestCase):

    def setUp(self):
        print("setUp")
        self.n = 10
    def tearDown(self):
        print("tearDown")
        del self.n
    @classmethod
    def setUpClass(cls):
        print("setUpClass")
    @classmethod
    def tearDownClass(cls):
        print("tearDownClass")
    def test_fib_assert_equal(self):
        self.assertEqual(fib(self.n), 55)
    def test_fib_assert_true(self):
        self.assertTrue(fib(self.n) == 55)

if __name__ == "__main__":
    unittest.main()

output:

$ python test.py
setup module
setUpClass
setUp
tearDown
.setUp
tearDown
.tearDownClass
teardown module

----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK

Different module of setUp & tearDown hierarchy

# test_module.py
from __future__ import print_function

import unittest

class TestFoo(unittest.TestCase):
    @classmethod
    def setUpClass(self):
        print("foo setUpClass")
    @classmethod
    def tearDownClass(self):
        print("foo tearDownClass")
    def setUp(self):
        print("foo setUp")
    def tearDown(self):
        print("foo tearDown")
    def test_foo(self):
        self.assertTrue(True)

class TestBar(unittest.TestCase):
    def setUp(self):
        print("bar setUp")
    def tearDown(self):
        print("bar tearDown")
    def test_bar(self):
        self.assertTrue(True)

# test.py
from __future__ import print_function

from test_module import TestFoo
from test_module import TestBar
import test_module
import unittest

def setUpModule():
    print("setUpModule")

def tearDownModule():
    print("tearDownModule")


if __name__ == "__main__":
    test_module.setUpModule = setUpModule
    test_module.tearDownModule = tearDownModule
    suite1 = unittest.TestLoader().loadTestsFromTestCase(TestFoo)
    suite2 = unittest.TestLoader().loadTestsFromTestCase(TestBar)
    suite = unittest.TestSuite([suite1,suite2])
    unittest.TextTestRunner().run(suite)

output:

$ python test.py
setUpModule
foo setUpClass
foo setUp
foo tearDown
.foo tearDownClass
bar setUp
bar tearDown
.tearDownModule

----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK

Run tests via unittest.TextTestRunner

>>> import unittest
>>> class TestFoo(unittest.TestCase):
...     def test_foo(self):
...         self.assertTrue(True)
...     def test_bar(self):
...         self.assertFalse(False)

>>> suite = unittest.TestLoader().loadTestsFromTestCase(TestFoo)
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_bar (__main__.TestFoo) ... ok
test_foo (__main__.TestFoo) ... ok

----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK

Test raise exception

>>> import unittest

>>> class TestRaiseException(unittest.TestCase):
...     def test_raise_except(self):
...         with self.assertRaises(SystemError):
...             raise SystemError
>>> suite_loader = unittest.TestLoader()
>>> suite = suite_loader.loadTestsFromTestCase(TestRaiseException)
>>> unittest.TextTestRunner().run(suite)
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
>>> class TestRaiseFail(unittest.TestCase):
...     def test_raise_fail(self):
...         with self.assertRaises(SystemError):
...             pass
>>> suite = unittest.TestLoader().loadTestsFromTestCase(TestRaiseFail)
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_raise_fail (__main__.TestRaiseFail) ... FAIL

======================================================================
FAIL: test_raise_fail (__main__.TestRaiseFail)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "<stdin>", line 4, in test_raise_fail
AssertionError: SystemError not raised

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (failures=1)

Pass arguments into a TestCase

>>> from __future__ import print_function
>>> import unittest
>>> class TestArg(unittest.TestCase):
...     def __init__(self, testname, arg):
...         super(TestArg, self).__init__(testname)
...         self._arg = arg
...     def setUp(self):
...         print("setUp:", self._arg)
...     def test_arg(self):
...         print("test_arg:", self._arg)
...         self.assertTrue(True)
...
>>> suite = unittest.TestSuite()
>>> suite.addTest(TestArg('test_arg', 'foo'))
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_arg (__main__.TestArg) ... setUp: foo
test_arg: foo
ok

----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Group multiple testcases into a suite

>>> import unittest
>>> class TestFooBar(unittest.TestCase):
...     def test_foo(self):
...         self.assertTrue(True)
...     def test_bar(self):
...         self.assertTrue(True)
...
>>> class TestHelloWorld(unittest.TestCase):
...     def test_hello(self):
...         self.assertEqual("Hello", "Hello")
...     def test_world(self):
...         self.assertEqual("World", "World")
...
>>> suite_loader = unittest.TestLoader()
>>> suite1 = suite_loader.loadTestsFromTestCase(TestFooBar)
>>> suite2 = suite_loader.loadTestsFromTestCase(TestHelloWorld)
>>> suite = unittest.TestSuite([suite1, suite2])
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_bar (__main__.TestFooBar) ... ok
test_foo (__main__.TestFooBar) ... ok
test_hello (__main__.TestHelloWorld) ... ok
test_world (__main__.TestHelloWorld) ... ok

----------------------------------------------------------------------
Ran 4 tests in 0.000s

OK

Group multiple tests from different TestCase

>>> import unittest
>>> class TestFoo(unittest.TestCase):
...     def test_foo(self):
...         assert "foo" == "foo"
...
>>> class TestBar(unittest.TestCase):
...     def test_bar(self):
...         assert "bar" == "bar"
...
>>> suite = unittest.TestSuite()
>>> suite.addTest(TestFoo('test_foo'))
>>> suite.addTest(TestBar('test_bar'))
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_foo (__main__.TestFoo) ... ok
test_bar (__main__.TestBar) ... ok

----------------------------------------------------------------------
Ran 2 tests in 0.001s

OK

Skip some tests in the TestCase

>>> import unittest
>>> RUN_FOO = False
>>> DONT_RUN_BAR = False
>>> class TestSkip(unittest.TestCase):
...     def test_always_run(self):
...         self.assertTrue(True)
...     @unittest.skip("always skip this test")
...     def test_always_skip(self):
...         raise RuntimeError
...     @unittest.skipIf(RUN_FOO == False, "demo skipIf")
...     def test_skipif(self):
...         raise RuntimeError
...     @unittest.skipUnless(DONT_RUN_BAR == True, "demo skipUnless")
...     def test_skipunless(self):
...         raise RuntimeError
...
>>> suite = unittest.TestLoader().loadTestsFromTestCase(TestSkip)
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_always_run (__main__.TestSkip) ... ok
test_always_skip (__main__.TestSkip) ... skipped 'always skip this test'
test_skipif (__main__.TestSkip) ... skipped 'demo skipIf'
test_skipunless (__main__.TestSkip) ... skipped 'demo skipUnless'

----------------------------------------------------------------------
Ran 4 tests in 0.000s

OK (skipped=3)

Monolithic Test

>>> from __future__ import print_function
>>> import unittest
>>> class Monolithic(unittest.TestCase):
...     def step1(self):
...         print('step1')
...     def step2(self):
...         print('step2')
...     def step3(self):
...         print('step3')
...     def _steps(self):
...         for attr in sorted(dir(self)):
...             if not attr.startswith('step'):
...                 continue
...             yield attr
...     def test_foo(self):
...         for _s in self._steps():
...             try:
...                 getattr(self, _s)()
...             except Exception as e:
...                 self.fail('{} failed({})'.format(attr, e))
...
>>> suite = unittest.TestLoader().loadTestsFromTestCase(Monolithic)
>>> unittest.TextTestRunner().run(suite)
step1
step2
step3
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
<unittest.runner.TextTestResult run=1 errors=0 failures=0>

Cross-module variables to Test files

test_foo.py

from __future__ import print_function

import unittest

print(conf)

class TestFoo(unittest.TestCase):
    def test_foo(self):
        print(conf)

    @unittest.skipIf(conf.isskip==True, "skip test")
    def test_skip(self):
        raise RuntimeError

test_bar.py

from __future__ import print_function

import unittest
import __builtin__

if __name__ == "__main__":
    conf = type('TestConf', (object,), {})
    conf.isskip = True

    # make a cross-module variable
    __builtin__.conf = conf
    module = __import__('test_foo')
    loader = unittest.TestLoader()
    suite = loader.loadTestsFromTestCase(module.TestFoo)
    unittest.TextTestRunner(verbosity=2).run(suite)

output:

$ python test_bar.py
<class '__main__.TestConf'>
test_foo (test_foo.TestFoo) ... <class '__main__.TestConf'>
ok
test_skip (test_foo.TestFoo) ... skipped 'skip test'

----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK (skipped=1)

skip setup & teardown when the test is skipped

>>> from __future__ import print_function
>>> import unittest
>>> class TestSkip(unittest.TestCase):
...     def setUp(self):
...         print("setUp")
...     def tearDown(self):
...         print("tearDown")
...     @unittest.skip("skip this test")
...     def test_skip(self):
...         raise RuntimeError
...     def test_not_skip(self):
...         self.assertTrue(True)
...
>>> suite = unittest.TestLoader().loadTestsFromTestCase(TestSkip)
>>> unittest.TextTestRunner(verbosity=2).run(suite)
test_not_skip (__main__.TestSkip) ... setUp
tearDown
ok
test_skip (__main__.TestSkip) ... skipped 'skip this test'

----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK (skipped=1)

Re-using old test code

>>> from __future__ import print_function
>>> import unittest
>>> def old_func_test():
...     assert "Hello" == "Hello"
...
>>> def old_func_setup():
...     print("setup")
...
>>> def old_func_teardown():
...     print("teardown")
...
>>> testcase = unittest.FunctionTestCase(old_func_test,
...                                      setUp=old_func_setup,
...                                      tearDown=old_func_teardown)
>>> suite = unittest.TestSuite([testcase])
>>> unittest.TextTestRunner().run(suite)
setup
teardown
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
<unittest.runner.TextTestResult run=1 errors=0 failures=0>

Testing your document is right

"""
This is an example of doctest

>>> fib(10)
55
"""

def fib(n):
""" This function calculate fib number.

Example:

    >>> fib(10)
    55
    >>> fib(-1)
    Traceback (most recent call last):
    ...
    ValueError
"""
if n < 0:
    raise ValueError('')
return 1 if n<=2 else fib(n-1) + fib(n-2)

if __name__ == "__main__":
    import doctest
    doctest.testmod()

output:

$ python demo_doctest.py -v
Trying:
fib(10)
Expecting:
55
ok
Trying:
fib(10)
Expecting:
55
ok
Trying:
fib(-1)
Expecting:
Traceback (most recent call last):
...
ValueError
ok
2 items passed all tests:
1 tests in __main__
2 tests in __main__.fib
3 tests in 2 items.
3 passed and 0 failed.
Test passed.

Re-using doctest to unittest

import unittest
import doctest

"""
This is an example of doctest

>>> fib(10)
55
"""

def fib(n):
    """ This function calculate fib number.

    Example:

        >>> fib(10)
        55
        >>> fib(-1)
        Traceback (most recent call last):
            ...
        ValueError
    """
    if n < 0:
        raise ValueError('')
    return 1 if n<=2 else fib(n-1) + fib(n-2)

if __name__ == "__main__":
    finder = doctest.DocTestFinder()
    suite = doctest.DocTestSuite(test_finder=finder)
    unittest.TextTestRunner(verbosity=2).run(suite)

output:

fib (__main__)
Doctest: __main__.fib ... ok

----------------------------------------------------------------------
Ran 1 test in 0.023s

OK

Customize test report

from unittest import (
        TestCase,
        TestLoader,
        TextTestResult,
        TextTestRunner)

from pprint import pprint
import unittest
import os

OK = 'ok'
FAIL = 'fail'
ERROR = 'error'
SKIP = 'skip'

class JsonTestResult(TextTestResult):

    def __init__(self, stream, descriptions, verbosity):
        super_class = super(JsonTestResult, self)
        super_class.__init__(stream, descriptions, verbosity)

        # TextTestResult has no successes attr
        self.successes = []

    def addSuccess(self, test):
        # addSuccess do nothing, so we need to overwrite it.
        super(JsonTestResult, self).addSuccess(test)
        self.successes.append(test)

    def json_append(self, test, result, out):
        suite = test.__class__.__name__
        if suite not in out:
            out[suite] = {OK: [], FAIL: [], ERROR:[], SKIP: []}
        if result is OK:
            out[suite][OK].append(test._testMethodName)
        elif result is FAIL:
            out[suite][FAIL].append(test._testMethodName)
        elif result is ERROR:
            out[suite][ERROR].append(test._testMethodName)
        elif result is SKIP:
            out[suite][SKIP].append(test._testMethodName)
        else:
            raise KeyError("No such result: {}".format(result))
        return out

    def jsonify(self):
        json_out = dict()
        for t in self.successes:
            json_out = self.json_append(t, OK, json_out)

        for t, _ in self.failures:
            json_out = self.json_append(t, FAIL, json_out)

        for t, _ in self.errors:
            json_out = self.json_append(t, ERROR, json_out)

        for t, _ in self.skipped:
            json_out = self.json_append(t, SKIP, json_out)

        return json_out

class TestSimple(TestCase):

    def test_ok_1(self):
        foo = True
        self.assertTrue(foo)

    def test_ok_2(self):
        bar = True
        self.assertTrue(bar)

    def test_fail(self):
        baz = False
        self.assertTrue(baz)

    def test_raise(self):
        raise RuntimeError

    @unittest.skip("Test skip")
    def test_skip(self):
        raise NotImplementedError

if __name__ == '__main__':
    # redirector default output of unittest to /dev/null
    with open(os.devnull, 'w') as null_stream:
        # new a runner and overwrite resultclass of runner
        runner = TextTestRunner(stream=null_stream)
        runner.resultclass = JsonTestResult

        # create a testsuite
        suite = TestLoader().loadTestsFromTestCase(TestSimple)

        # run the testsuite
        result = runner.run(suite)

        # print json output
        pprint(result.jsonify())

output:

$ python test.py
{'TestSimple': {'error': ['test_raise'],
                'fail': ['test_fail'],
                'ok': ['test_ok_1', 'test_ok_2'],
                'skip': ['test_skip']}}

Mock - using @patch substitute original method

# python-3.3 or above

>>> from unittest.mock import patch
>>> import os
>>> def fake_remove(path, *a, **k):
...     print("remove done")
...
>>> @patch('os.remove', fake_remove)
... def test():
...     try:
...         os.remove('%$!?&*') # fake os.remove
...     except OSError as e:
...         print(e)
...     else:
...         print('test success')
...
>>> test()
remove done
test success

Note

Without mock, above test will always fail.

>>> import os
>>> def test():
...     try:
...         os.remove('%$!?&*')
...     except OSError as e:
...         print(e)
...     else:
...         print('test success')
...
>>> test()
[Errno 2] No such file or directory: '%$!?&*'

What with unittest.mock.patch do?

from unittest.mock import patch
import os

PATH = '[email protected]!%?&'

def fake_remove(path):
    print("Fake remove")


class SimplePatch:

    def __init__(self, target, new):
        self._target = target
        self._new = new

    def get_target(self, target):
        target, attr = target.rsplit('.', 1)
        getter = __import__(target)
        return getter, attr

    def __enter__(self):
        orig, attr = self.get_target(self._target)
        self.orig, self.attr = orig, attr
        self.orig_attr = getattr(orig, attr)
        setattr(orig, attr, self._new)
        return self._new

    def __exit__(self, *exc_info):
        setattr(self.orig, self.attr, self.orig_attr)
        del self.orig_attr


print('---> inside unittest.mock.patch scope')
with patch('os.remove', fake_remove):
    os.remove(PATH)

print('---> inside simple patch scope')
with SimplePatch('os.remove', fake_remove):
    os.remove(PATH)

print('---> outside patch scope')
try:
    os.remove(PATH)
except OSError as e:
    print(e)

output:

$ python3 simple_patch.py
---> inside unittest.mock.patch scope
Fake remove
---> inside simple patch scope
Fake remove
---> outside patch scope
[Errno 2] No such file or directory: '[email protected]!%?&'

Mock - substitute open

>>> import urllib
>>> from unittest.mock import patch, mock_open
>>> def send_req(url):
...     with urllib.request.urlopen(url) as f:
...         if f.status == 200:
...             return f.read()
...         raise urllib.error.URLError
...
>>> fake_html = b'<html><h1>Mock Content</h1></html>'
>>> mock_urlopen = mock_open(read_data=fake_html)
>>> ret = mock_urlopen.return_value
>>> ret.status = 200
>>> @patch('urllib.request.urlopen', mock_urlopen)
... def test_send_req_success():
...     try:
...         ret = send_req('http://www.mockurl.com')
...         assert ret == fake_html
...     except Exception as e:
...         print(e)
...     else:
...         print('test send_req success')
...
>>> test_send_req_success()
test send_req success
>>> ret = mock_urlopen.return_value
>>> ret.status = 404
>>> @patch('urllib.request.urlopen', mock_urlopen)
... def test_send_req_fail():
...     try:
...         ret = send_req('http://www.mockurl.com')
...         assert ret == fake_html
...     except Exception as e:
...         print('test fail success')
...
>>> test_send_req_fail()
test fail success