Python assertEqual
Summary: in this tutorial, you’ll learn how to use the Python assertEqual() method to test if two values are equal.
Introduction to the Python assertEqual() method
The assertEqual()assertEqual()
assertEqual(first, second, msg=None)Code language: Python (python)
If the first value does not equal the second value, the test will fail.
The msg is optional. If the msg is provided, it’ll be shown on the test result if the test fails.
Python assertEqual() method example
First, create a new module called main.py and define the add() function:
def add(a, b):
return a + bCode language: Python (python)
Second, create a test module test_main.py to test the add() function:
import unittestfrom main import add
class TestMain(unittest.TestCase):
def test_add(self):
self.assertEqual(add(1, 2), 3)
Code language: Python (python)
Third, run the test:
python -m unittest test_main.py -vCode language: Python (python)
Output:
test_add (test_main.TestMain) ... ok----------------------------------------------------------------------
Ran 1 test in 0.000s
OK
Code language: Python (python)
Python assertNotEqual() method
The assertNotEqual() method tests if two values are not equal:
assertNotEqual(first, second, msg=None)Code language: Python (python)
If the first is equal to the second, the test will fail. Otherwise, it’ll pass. For example:
import unittestfrom main import add
class TestMain(unittest.TestCase):
def test_add(self):
self.assertEqual(add(1, 2), 3)
def test_add_floats(self):
self.assertNotEqual(add(0.2, 0.1), 0.3)
Code language: Python (python)
Run the test:
python -m unittest test_main.py -vCode language: Python (python)
Output:
test_add (test_main.TestMain) ... ok
test_add_floats (test_main.TestMain) ... ok----------------------------------------------------------------------
Ran 2 tests in 0.001s
OK
Code language: Python (python)
Since 0.2 + 0.1 returns 0.30000000000000004, it’s not equal to 0.3. Therefore, the following test passes:
self.assertNotEqual(add(0.2, 0.1), 0.3)Code language: Python (python)
Summary
- Use the
assertEqual()method to test if two values are equal. - Use the
assertNotEqual()method to test if two values are not equal.