The Birds are coming!!! Close your windows.: The Python unit testing framework

The PyUnit is a unit testing framework, which is a Python implementation of famous JUnit, which is the de facto standard unit testing framework for its different language.

Python implements this standard unit testing with the module unittest.

Firstly, a piece of theory on testing

In order to design a comprehensive testing plan we want to take advantage of the following types of tests:

unit-testing
    Testing done on a single subroutine or module.
functional-testing
    Testing for a given functional group of subroutines or modules, for example, testing model dynamics alone without the model physics.
system-testing
    Testing done on the whole system.

In particular, proper unit-tests will do the following:

Applicable requirements are checked.
Exercise every line of code.
Check that the full range of possible input data works.
Boundary analysis - logical statements that refer to threshold states are checked to ensure they are correct.
Check for bad input data.

A test case in Python is created by subclassing unittest.TestCase.
- a setUp() method is defined, the test runner will run that method prior to each test.
- a tearDown() method is defined, the test runner will invoke that method after each test. I

Main assert functions:

assertEqual(a, b) a == b
assertNotEqual(a, b) a != b
assertTrue(x) bool(x) is True
assertFalse(x) bool(x) is False

Tthere are another assert function, and in particular in the following example we are going to use to test assert raised (assertRaises)

A suite is a group of test cases.

Finally, we are going to show an example of an independet class (TestKelvinToFahrenheit) that performeces the unit tests

File kelvinToFahrenheitFunctions.py - Function to be tested

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def KelvinToFahrenheit(Temperature):
    assert (Temperature >= 0), "Colder than absolute zero!"
    return ((Temperature - 273) * 1.8) + 32

File kelvinToFahrenheit.py Main function that only prints different values

#!/usr/bin/env python
  
import kelvinToFahrenheitFunctions as k2f

if __name__ == '__main__':
    print k2f.KelvinToFahrenheit(273)
    print k2f.KelvinToFahrenheit(104)
    print k2f.KelvinToFahrenheit(454)
    print int(k2f.KelvinToFahrenheit(505.78))
    print k2f.KelvinToFahrenheit(-5)

File TestKelvinToFahrenheit.py - Independent class and file to testing function kelvinToFahrenheit

#!/usr/bin/env python

import unittest
import math

import kelvinToFahrenheitFunctions as k2f

class TestKelvinToFahrenheit (unittest.TestCase):
    # Test positive value, for instance 104 and 454
    def test_positive_value (self):
        fahr_temp = k2f.KelvinToFahrenheit(104)
        self.assertEqual(fahr_temp, -272.2)
        fahr_temp = k2f.KelvinToFahrenheit(454)
        self.assertEqual(fahr_temp, 357.8)

    # Test boundary value 273 and 0
    def test_boundary_value (self):
        fahr_temp = k2f.KelvinToFahrenheit(273)
        self.assertEqual(fahr_temp, 32)
        fahr_temp = math.ceil(k2f.KelvinToFahrenheit(255.22))
        self.assertEqual(fahr_temp, 0)

    # Test assert raises, in this case colder than absolute zero
    # something impossible.
    def test_colder_abs_zero (self):
        self.assertRaises(AssertionError,
                            k2f.KelvinToFahrenheit,
                            - 1)

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

The output would be

$ ./TestKelvinToFahrenheit.py

...

----------------------------------------------------------------------

Ran 3 tests in 0.001s

OK

and with the --verbose option

$ ./TestKelvinToFahrenheit.py --verbose

test_boundary_value (__main__.TestKelvinToFahrenheit) ... ok

test_colder_abs_zero (__main__.TestKelvinToFahrenheit) ... ok

test_positive_value (__main__.TestKelvinToFahrenheit) ... ok

----------------------------------------------------------------------

Ran 3 tests in 0.001s

OK

OK