Declares a test method that the unittest framework will discover and execute to validate addition behavior.

Signals to the test runner and readers that this method constitutes a test case for addition functionality.

When writing a unit test for an addition function or method, typically inside a class that inherits from unittest.TestCase.

Inside a test module, within a class subclassing unittest.TestCase, often alongside setUp, tearDown, and other test methods.

def test_<method_name>(self): where <method_name> starts with 'test_' and describes the behavior under test.

def <method_name>(self): with the method name conventionally beginning with 'test_' for unittest discovery.

• unittest.TestCase
• assertEqual
• assertAlmostEqual
• setUp
• tearDown
• test suite runner

• Using pytest style: def test_addition(): (no self) – simpler but requires pytest instead of unittest
• Using descriptive name without 'test_' prefix: def addition_test(self): – not auto‑discovered by unittest unless renamed
• Adding parameters: def test_addition(self
• a
• b): – enables parametrization but needs a test generator or subTest.

Forgetting the self parameter (def test_addition():) – causes TypeError when unittest binds the method to an instance; Omitting the leading 'test_' in the method name (def addition(self):) – test is not discovered and never runs; Forgetting the colon at the end (def test_addition(self)) – syntax error, preventing module import; Using plain assert instead of self.assertEqual (assert a+b == 3) – may be suppressed by optimizer and lacks unittest reporting; Forgetting to import unittest or inherit from TestCase – leads to AttributeError when the test runner expects test methods.

def test_subtraction(self): – tests subtraction rather than addition; def test_addition(self, a, b): – parametrized test accepting arguments, differing by requiring a data provider; def benchmark_addition(self): – measures performance instead of correctness; def setUp(self): – runs before each test to prepare fixtures, differing in purpose (setup vs verification).

Coming from Java: may omit the self parameter, thinking of an implicit this → include self as the first parameter to bind the method to the test instance; Coming from pytest: may forget to inherit from unittest.TestCase or use pytest fixtures, leading to missing test discovery → either inherit from TestCase or adopt pytest‑style function tests; Coming from C: may expect function‑level tests without classes → wrap tests in a class or switch to pytest’s function‑based style.

• def test_subtraction(self):
• def test_multiplication(self):
• def setUp(self):
• def tearDown(self):
• def test_addition(self
• *args):

Do not use this pattern for non‑test helper methods; naming them with test_ prefix may cause unintended test execution; Performance impact is negligible as method definition overhead is minimal; Boundary condition: if the method name does not start with 'test_' (case‑sensitive) unittest will ignore it, even if the method contains assertions.

Ensures the test is automatically discovered and executed by unittest, providing reliable regression detection for addition logic and supporting test‑driven development.

Defining a test method is like writing a lab experiment protocol: you outline the exact steps to verify that addition behaves as expected.

The method must reside within a subclass of unittest.TestCase; test discovery relies on the method name matching the pattern test* (case‑sensitive).