Test file and function naming conventions in PyTest - Build an Automation Script

Verify pytest recognizes test files and functions by naming conventions

Preconditions (2)

Step 1: Create a Python file named test_sample.py

Step 2: Inside test_sample.py, define a function named test_addition

Step 3: In test_addition, write an assertion that 2 + 2 equals 4

Step 4: Run pytest on the project folder

Step 5: Observe which tests pytest discovers and runs

✅ Expected Result: pytest discovers and runs the test_addition function inside test_sample.py and reports the test as passed

Automation Requirements - pytest

Assertions Needed:

Verify pytest discovers test files starting with 'test_'

Verify pytest discovers test functions starting with 'test_'

Verify the test function runs and passes

Best Practices:

Name test files starting with 'test_' and ending with '.py'

Name test functions starting with 'test_'

Use simple assert statements for validations

Keep test functions small and focused

Automated Solution

PyTest

import pytest

def test_addition():
    assert 2 + 2 == 4

# To run this test, save it in a file named test_sample.py
# Then run: pytest

# pytest will automatically discover this test because the file and function names start with 'test_'

The code defines a test function named test_addition inside a file named test_sample.py. This follows pytest's naming conventions.

pytest automatically finds files starting with test_ and functions starting with test_. The assertion checks a simple math operation.

When you run pytest, it discovers and runs this test, reporting success if the assertion passes.

Common Mistakes - 3 Pitfalls

{'mistake': "Naming test files without the 'test_' prefix, e.g., sample_test.py", 'why_bad': "pytest will not discover files that do not start with 'test_', so tests inside won't run.", 'correct_approach': "Always name test files starting with 'test_', like test_sample.py."}

{'mistake': "Naming test functions without the 'test_' prefix, e.g., addition_test()", 'why_bad': "pytest ignores functions that do not start with 'test_', so the test won't execute.", 'correct_approach': "Name test functions starting with 'test_', like test_addition()."}

Using print statements instead of assert for validations

Bonus Challenge

Now create three test functions in the same file to test addition, subtraction, and multiplication using correct naming conventions.

Show Hint

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