Test file and function naming conventions in PyTest - Test Execution Trace

Test Overview

This test checks that pytest recognizes test files and test functions based on proper naming conventions. It verifies that a test function named with the prefix test_ inside a file named with the prefix test_ is discovered and executed by pytest.

Test Code - PyTest

PyTest

import pytest

def test_addition():
    assert 2 + 3 == 5

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Pytest starts and scans the current directory for test files matching pattern 'test_*.py' or '*_test.py'.	Test file named 'test_example.py' is present with the test function inside.	—	PASS
2	Pytest loads 'test_example.py' and discovers the function 'test_addition' because it starts with 'test_'.	Test function 'test_addition' is ready to run.	—	PASS
3	Pytest executes the function 'test_addition'.	Inside the test function, the expression 2 + 3 == 5 is evaluated.	Assert that 2 + 3 equals 5.	PASS
4	Pytest reports the test result as passed.	Test run completes successfully with no failures.	—	PASS

Failure Scenario

Failing Condition: Test function or file does not follow pytest naming conventions (e.g., function not starting with 'test_').

Execution Trace Quiz - 3 Questions

Why does pytest not run a function named 'addition_test' inside 'test_example.py'?

A Because the file name does not start with 'test_'.

B Because the function name does not start with 'test_'.

C Because pytest only runs functions inside classes.

D Because the function is missing an assert statement.

Key Result

Following pytest's naming conventions for test files and functions is essential for automatic test discovery and execution.

Practice

1. Which of the following is a correct name for a pytest test file?

easy

A. test_example.py

B. example_tested.py

C. example.py

D. mytestfile.py

Solution

1. Step 1: Understand pytest file naming rules

   Pytest requires test files to start with test_ or end with _test.py.

2. Step 2: Check each option against the rule

   test_example.py starts with test_, so it is correct. Options A, C, and D do not follow the naming convention.

3. Final Answer:

   test_example.py -> Option A

4. Quick Check:

   File starts with 'test_' = B [OK]

Hint: Test files start with 'test_' or end with '_test.py' [OK]

Common Mistakes:

• Naming file without 'test_' prefix or '_test.py' suffix
• Using generic file names without test indication
• Confusing test function naming with file naming

2. Which of the following is the correct way to name a pytest test function?

easy

A. login_test()

B. check_login()

C. test_login()

D. TestLogin()

Solution

1. Step 1: Recall pytest function naming rule

   Pytest requires test functions to start with test_ to be discovered automatically.

2. Step 2: Evaluate each function name

   Only test_login() starts with test_. Others do not follow the rule.

3. Final Answer:

   test_login() -> Option C

4. Quick Check:

   Function starts with 'test_' = A [OK]

Hint: Test functions must start with 'test_' [OK]

Common Mistakes:

• Omitting 'test_' prefix in function names
• Using camel case instead of snake case
• Confusing test file and function naming rules

3. Given the following test file named test_math.py with this code:

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

def test_add():
    assert add(2, 3) == 5

What will pytest do when run on this file?

medium

A. Run the test function and fail

B. Run the test function and pass

C. Skip the test function

D. Raise a syntax error

Solution

1. Step 1: Check file and function naming

   The file is named test_math.py and the function is named test_add, both following pytest conventions.

2. Step 2: Analyze test function behavior

   The test asserts add(2, 3) == 5, which is true, so the test will pass.

3. Final Answer:

   Run the test function and pass -> Option B

4. Quick Check:

   Correct naming + passing assertion = A [OK]

Hint: Correct names run tests; passing asserts pass tests [OK]

Common Mistakes:

• Misnaming test functions so pytest skips them
• Assuming test fails without checking assertion
• Confusing syntax errors with test failures

4. You have a test file named math_test.py with a function named add_test(). When running pytest, no tests are found. What is the most likely cause?

medium

A. The function name does not start with 'test_'

B. The file extension is incorrect

C. The file name does not start with 'test_'

D. The test function has no assert statement

Solution

1. Step 1: Check file naming

   The file math_test.py ends with _test.py, which is valid for pytest discovery.

2. Step 2: Check function naming

   The function is named add_test(), which does not start with test_. Pytest ignores such functions.

3. Final Answer:

   The function name does not start with 'test_' -> Option A

4. Quick Check:

   Function must start with 'test_' = C [OK]

Hint: Function names must start with 'test_' to be found [OK]

Common Mistakes:

• Assuming file name alone is enough
• Naming functions with '_test' suffix instead of prefix
• Forgetting to add assert statements

5. You want pytest to automatically discover and run tests in your project. Which combination of file and function names will ensure this?

• File: example_test.py
• Functions: test_case1(), case2_test(), test_case3()

Which functions will pytest run?

hard

A. None of the functions

B. Only case2_test()

C. All three functions

D. Only test_case1() and test_case3()

Solution

1. Step 1: Confirm file naming

   The file example_test.py ends with _test.py, so pytest will discover it.

2. Step 2: Check function naming rules

   Pytest runs functions starting with test_. So test_case1() and test_case3() will run. case2_test() will be ignored.

3. Final Answer:

   Only test_case1() and test_case3() -> Option D

4. Quick Check:

   Functions start with 'test_' run = D [OK]

Hint: File ends '_test.py'; functions start 'test_' to run [OK]

Common Mistakes:

• Thinking '_test' suffix in function name triggers test
• Assuming all functions in test files run automatically
• Confusing file and function naming rules