{"id":423,"date":"2024-01-29T11:08:00","date_gmt":"2024-01-29T11:08:00","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=423"},"modified":"2024-01-29T11:08:02","modified_gmt":"2024-01-29T11:08:02","slug":"python-assertisnone","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/29\/python-assertisnone\/","title":{"rendered":"Python assertIsNone()"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you\u2019ll learn how to use the Python assertIsNone()<\/code> method to test if an expression is None<\/code>.<\/p>\n\n\n\n

Introduction to the Python assertIsNone() method<\/h2>\n\n\n\n

The\u00a0assertIsNone()<\/code>\u00a0is a method of the\u00a0TestCase<\/code>\u00a0class of the\u00a0unittest\u00a0module. The\u00a0assertIsNone()<\/code>\u00a0test if an expression is\u00a0None:<\/p>\n\n\n\n

assertIsNone(expr, msg=None)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
If the expr<\/code> is None<\/code>, the test passes. Otherwise, the test will fail.<\/p>\n\n\n\n
The msg<\/code> is optional. It\u2019ll be displayed in the test result if the test fails.<\/p>\n\n\n\n
Python assertIsNone() method examples<\/h2>\n\n\n\n
Let\u2019s take some examples of using the assertIsNone()<\/code> method.<\/p>\n\n\n\n
1) Using assertIsNone() with a success case<\/h3>\n\n\n\n
The following example uses the\u00a0assertIsNone()<\/code>\u00a0to test if the message variable is None:<\/p>\n\n\n\n
import unittest class TestNone(unittest.TestCase): def test_variable_none(self): message = None self.assertIsNone(message)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Run the test:<\/p>\n\n\n\n
python -m unittest -v<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
test_variable_none (test_none.TestNone) ... ok ---------------------------------------------------------------------- Ran 1 test in 0.000s<\/code>Code language: plaintext (plaintext)<\/small><\/code><\/pre>\n\n\n\n
2) Using assertIsNone() with a failed case<\/h3>\n\n\n\n
The following example uses the\u00a0assertIsNone()<\/code>\u00a0method to test if the\u00a0message<\/code>\u00a0variable is None:<\/p>\n\n\n\n
import unittest class TestNone(unittest.TestCase): def test_variable_not_none(self): message = 'Hello' self.assertIsNone(message)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Run the test:<\/p>\n\n\n\n
python -m unittest -v<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
test_variable_not_none (test_none.TestNone) ... FAIL ====================================================================== FAIL: test_variable_not_none (test_none.TestNone) ---------------------------------------------------------------------- Traceback (most recent call last): File \"D:\\python-unit-testing\\test_none.py\", line 7, in test_variable_not_none self.assertIsNone(message) AssertionError: 'Hello' is not None ---------------------------------------------------------------------- Ran 1 test in 0.001s FAILED (failures=1)<\/code>Code language: plaintext (plaintext)<\/small><\/code><\/pre>\n\n\n\n
Since the message is 'Hello'<\/code>, it is not None. Therefore, the test failed.<\/p>\n\n\n\n
3) Using assertIsNone() with a failed case with a message<\/h3>\n\n\n\n
The following example uses the\u00a0assertIsNone()<\/code>\u00a0to test if the message variable is None. Also, we show a message when the test fails:<\/p>\n\n\n\n
import unittest class TestNone(unittest.TestCase): def test_variable_not_none(self): message = 'Hello' self.assertIsNone( message, f'The message is \"{message}\" so it is not None.' )<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Run the test:<\/p>\n\n\n\n
python -m unittest -v<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
test_variable_not_none (test_none.TestNone) ... FAIL ====================================================================== FAIL: test_variable_not_none (test_none.TestNone) ---------------------------------------------------------------------- Traceback (most recent call last): File \"D:\\python-unit-testing\\test_none.py\", line 7, in test_variable_not_none self.assertIsNone( AssertionError: 'Hello' is not None : The message is \"Hello\" so it is not None. ---------------------------------------------------------------------- Ran 1 test in 0.001s FAILED (failures=1)<\/code>Code language: plaintext (plaintext)<\/small><\/code><\/pre>\n\n\n\n
Python assertIsNotNone() method<\/h2>\n\n\n\n
The\u00a0assertIsNotNone()<\/code>\u00a0is opposite of the\u00a0assertIsNone()<\/code>\u00a0method. The\u00a0assertIsNotNone()<\/code>\u00a0method tests if a variable is not None.<\/p>\n\n\n\n
assertIsNotNone(expr, msg=None)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
The test passes if the\u00a0expr<\/code>\u00a0is not\u00a0None<\/code>\u00a0or fails otherwise. For example:<\/p>\n\n\n\n
import unittest class TestNone(unittest.TestCase): def test_variable_is_not_none(self): message = 'Bye' self.assertIsNotNone(message)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Run the test:<\/p>\n\n\n\n
python -m unittest -v<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
Output:<\/p>\n\n\n\n
test_variable_is_not_none (test_not_none.TestNone) ... ok ---------------------------------------------------------------------- Ran 1 test in 0.001s OK<\/code><\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
Summary: in this tutorial, you\u2019ll learn how to use the Python assertIsNone() method to test if an expression is None. Introduction to the Python assertIsNone() method The\u00a0assertIsNone()\u00a0is a method of the\u00a0TestCase\u00a0class of the\u00a0unittest\u00a0module. The\u00a0assertIsNone()\u00a0test if an expression is\u00a0None: If the expr is None, the test passes. Otherwise, the test will fail. The msg is optional. It\u2019ll be displayed in the test result if […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[43],"tags":[],"class_list":["post-423","post","type-post","status-publish","format-standard","hentry","category-3-python-unit-testing"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/423","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=423"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/423\/revisions"}],"predecessor-version":[{"id":424,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/423\/revisions\/424"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=423"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=423"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=423"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}