Python Unit Testing with unittest: Reference and Examples
Last updated:Table of Contents
- Basic testing
- Assert exception is raised
- Run a single test from a class
- Group tests in suit
- Assert print output
Basic testing
.
├── mylib.py
│
└── mytest.py
# mylib.py
def sum_integers(a,b):
return a+b
# mytest.py
import unittest
import mylib
class MyTests(unittest.TestCase):
def test1(self):
# test code here
expected = 100
actual = mylib.sum_integers(50,50)
self.assertEqual(expected, actual, "summing 50 and 50 must equal 100")
if __name__ == '__main__':
unittest.main()
Save this file as mytest.py and call it as you would a regular script:
$ python mytest.py
.
----------------------------------------------------------------------
Ran 1 test in 0.000s
OK
Assert exception is raised
The code within the with block must raise an exception, or else the test case fails.
import unittest
import mylibs
class MyTests(unittest.TestCase):
def testException(self):
with self.assertRaises(IOError):
# this raises an exception
mylibs.methodThatRaisesException('some input')
if __name__ == '__main__':
unittest.main()
Run a single test from a class
Pass the class name and the method names as command-line arguments.
For example:
If mytests.py has the following contents:
# mytests.py
import unittest
class MyTests(unittest.TestCase):
def test1(self):
# test code here
pass
def test2(self):
# test code here
pass
class MyOtherTests(unittest.TestCase):
def test1(self):
# test code here
pass
def test2(self):
# test code here
pass
if __name__ == '__main__':
unittest.main()
To run all tests in the file:
$ python mytests.py.
To run all tests in class MyTests:
$ python mytests.py MyTests
To run just test2 in class MyOtherTests:
$ python mytests.py MyOtherTests.test1
Group tests in suit
Create a file called run_all_tests.py and add all tests from other files into it:
# run_all_tests.py
import unittest
# let MyTests and MyOtherTests be class that inherit from
# unittest.TestCase as in the examples above
from mytests import MyTests
from mytests import MyOtherTests
suite1 = unittest.TestLoader().loadTestsFromTestCase(MyTests)
suite2 = unittest.TestLoader().loadTestsFromTestCase(MyOtherTests)
all_tests = unittest.TestSuite([suite1, suite2])
unittest.TextTestRunner().run(all_tests)
Running:
$ python run_all_tests.py
....
----------------------------------------------------------------------
Ran 4 tests in 0.000s
OK