Python Unit Tests

= Python unit tests :hp-tags: python, unit tests

==== Why ?

You know why because if you don’t what are you doing here ?

==== Using unittest library

===== A basic example :

[source,python]

import unittest

def f1(a, b): return a + b

class TestF1(unittest.TestCase): ‘’’ This class will test f1 ‘’’

def test_f1(self):
    res = f1(2, 4)
    self.assertEqual(res, 6)

if name == ‘main’: unittest.main() —-

And this will result in :

---

Ran 1 test in 0.001s OK —-

===== What happens if the test fails :

[source, python]

# modify the value in the assertEqual
def test_f1(self):
    res = f1(2, 4)
    self.assertEqual(res, 3) ----

The output is now :

---

====================================================================== FAIL: test_f1 (tmp.TestF1) ———————————————————————- Traceback (most recent call last): File “C:\Users\rhz\PycharmProjects\panda\tmp.py”, line 16, in test_f1 self.assertEqual(res, 3) AssertionError: 6 != 3

---

Ran 1 test in 0.001s

FAILED (failures=1) Process finished with exit code 0 —-

===== Using setUp and tearDown

The doc says :

• setUp(): method called to prepare the test fixture. This is called immediately before calling the test method

• tearDown(): method called immediately after the test method has been called and the result recorded. This is called even if the test method raised an exception

This is a stupid example because here setUp is sufficient but in more complex situation tearDown alows us to clean the thing after a test or to do whatever you want.

[source, python]

def f1(a, b): return a + b

class TestF1(unittest.TestCase): ‘’’ This class will test f1 ‘’’

def setUp(self):
    self.good_value = 6

def tearDown(self):
    self.good_value = 6

def test_f1(self):
    res = f1(2, 4)
    self.assertEqual(res, self.good_value)

def test_f1_with_bad_value(self):
    res = f1(2, 4)
    self.good_value = 3
    self.assertEqual(res, self.good_value)

if name == ‘main’: unittest.main() —-

The output :

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====================================================================== FAIL: test_f1_with_bad_value (tmp.TestF1) ———————————————————————- Traceback (most recent call last): File “C:\Users\rhz\PycharmProjects\untitled\tmp.py”, line 23, in test_f1_with_bad_value self.assertEqual(res, self.good_value) AssertionError: 6 != 3

---

Ran 2 tests in 0.001s

FAILED (failures=1)

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:hide-uri-scheme: Url to the doc : https://docs.python.org/3/library/unittest.html#test-cases