Custom markers in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest with custom marker skip

What will be the output when running this pytest code with the custom marker @pytest.mark.skip(reason="Not ready") applied to test_feature()?

PyTest

import pytest

@pytest.mark.skip(reason="Not ready")
def test_feature():
    assert 1 == 1

def test_other():
    assert 2 == 2

A Both tests run and pass; overall result: 2 passed

B test_feature raises an error; test_other passes; overall result: 1 passed, 1 error

C test_feature fails due to skip marker; test_other passes; overall result: 1 passed, 1 failed

D test_feature is skipped; test_other passes; overall result: 1 passed, 1 skipped

💡 Hint

The skip marker prevents the test from running but counts as skipped, not failed.

The @pytest.mark.skip marker tells pytest to skip the test. The test is not run, so it neither passes nor fails. The other test runs and passes normally. The test report shows one passed and one skipped test.

❓ assertion

intermediate

Correct assertion for custom marker usage

Which assertion correctly verifies that a test function is marked with a custom marker named slow in pytest?

PyTest

import pytest

def test_example():
    pass

# Assume test_example is marked with @pytest.mark.slow

A assert test_example.has_marker('slow')

B assert any(marker.name == 'slow' for marker in test_example.pytestmark)

C assert 'slow' in test_example.pytestmark

D assert test_example.marker == 'slow'

💡 Hint

pytest stores markers as objects with a name attribute in the pytestmark list.

pytest stores markers in a list called pytestmark attached to the test function. Each marker is an object with a name attribute. To check if a marker named 'slow' is present, you must check if any marker's name equals 'slow'.

🔧 Debug

advanced

Debugging marker registration error

Given this pytest configuration snippet, what is the cause of the error when trying to use the custom marker integration?

PyTest

# content of pytest.ini
[pytest]
markers =
    integration: mark test as integration test

# test_sample.py
import pytest

@pytest.mark.integration
def test_api():
    assert True

A Indentation error before test_api function definition causes syntax error

B Marker 'integration' is not registered in pytest.ini

C Missing import of integration marker causes NameError

D pytest.ini file is ignored unless placed in root directory

💡 Hint

Check the indentation of the test function definition line.

The test function test_api has an extra space before its definition line, causing an IndentationError. This prevents pytest from running the test and using the marker properly.

❓ framework

advanced

Using custom markers to select tests

Which pytest command line option runs only tests marked with the custom marker database?

A pytest -m database

B pytest --run-database

C pytest --markers=database

D pytest -k database

💡 Hint

The -m option filters tests by marker expression.

The -m option in pytest runs tests that match the given marker expression. Using pytest -m database runs only tests marked with @pytest.mark.database.

🧠 Conceptual

expert

Best practice for custom marker documentation

Why is it important to declare custom markers in the pytest.ini file under the markers section?

A To allow markers to be used only in test classes but not in functions

B To register markers as built-in pytest markers for performance optimization

C To avoid pytest warnings about unknown markers and provide documentation for users

D To enable pytest to automatically skip tests with those markers

💡 Hint

pytest warns if it encounters markers not declared in configuration.

Declaring custom markers in pytest.ini under the markers section prevents pytest from showing warnings about unknown markers. It also serves as documentation for other developers about the purpose of each marker.

Practice

1. What is the main purpose of using custom markers in pytest?

easy

A. To generate test data automatically

B. To change the Python interpreter version

C. To automatically fix test failures

D. To label tests for grouping and selective running

Solution

1. Step 1: Understand what custom markers do

   Custom markers in pytest are used to tag tests with labels for easier management.

2. Step 2: Identify the purpose of these labels

   These labels help run specific groups of tests selectively using the marker name.

3. Final Answer:

   To label tests for grouping and selective running -> Option D

4. Quick Check:

   Custom markers = test grouping [OK]

Hint: Markers tag tests to run groups easily [OK]

Common Mistakes:

• Thinking markers change Python version
• Assuming markers fix test errors automatically
• Confusing markers with test data generation

2. Which of the following is the correct syntax to mark a test with a custom marker named slow?

easy

A. @pytest.mark.slow\ndef test_example(): pass

B. @pytest.slow.mark\ndef test_example(): pass

C. @pytest.mark[slow]\ndef test_example(): pass

D. @pytest.mark('slow')\ndef test_example(): pass

Solution

1. Step 1: Recall pytest marker syntax

   Custom markers use dot notation: @pytest.mark.markername before the test function.

2. Step 2: Match the correct syntax

   @pytest.mark.slow is the correct way to apply the 'slow' marker.

3. Final Answer:

   @pytest.mark.slow\ndef test_example(): pass -> Option A

4. Quick Check:

   Marker syntax = @pytest.mark.name [OK]

Hint: Use dot notation: @pytest.mark.name [OK]

Common Mistakes:

• Using parentheses instead of dot notation
• Using square brackets instead of dot notation
• Placing marker after function name

3. Given the following test file, what will be the output when running pytest -m slow?

import pytest

@pytest.mark.slow
def test_a():
    assert True

def test_b():
    assert True

@pytest.mark.slow
def test_c():
    assert False

medium

A. Runs all tests; test_c fails

B. Runs only test_b; all pass

C. Runs test_a and test_c; test_c fails, test_a passes

D. Runs test_a and test_b; all pass

Solution

1. Step 1: Understand what pytest -m slow does

   This command runs only tests marked with the 'slow' marker.

2. Step 2: Identify marked tests in the code

   test_a and test_c have @pytest.mark.slow, so only these run.

3. Step 3: Check test results

   test_a passes (assert True), test_c fails (assert False).

4. Final Answer:

   Runs test_a and test_c; test_c fails, test_a passes -> Option C

5. Quick Check:

   pytest -m slow runs marked tests only [OK]

Hint: -m runs only tests with that marker [OK]

Common Mistakes:

• Assuming all tests run with -m option
• Ignoring test failures in marked tests
• Running unmarked tests by mistake

4. What is wrong with this pytest marker usage?

import pytest

@pytest.mark.slow()
def test_example():
    assert True

medium

A. Markers should not have parentheses unless parameters are used

B. Marker name must be uppercase

C. The test function must have parameters

D. pytest.mark cannot be used on test functions

Solution

1. Step 1: Check marker syntax

   Markers without parameters should not have parentheses; @pytest.mark.slow() is incorrect.

2. Step 2: Correct usage

   Use @pytest.mark.slow without parentheses for simple markers.

3. Final Answer:

   Markers should not have parentheses unless parameters are used -> Option A

4. Quick Check:

   Use parentheses only with marker args [OK]

Hint: No parentheses for simple markers [OK]

Common Mistakes:

• Adding empty parentheses to markers
• Using uppercase marker names incorrectly
• Thinking markers require function parameters

5. You want to run tests marked as database but exclude those also marked as slow. Which pytest command achieves this?

hard

A. pytest -m "database or slow"

B. pytest -m "database and not slow"

C. pytest -m "not database and slow"

D. pytest -m "database and slow"

Solution

1. Step 1: Understand marker expressions

   pytest supports boolean expressions with markers: and, or, not.

2. Step 2: Formulate the correct expression

   To run tests marked 'database' but exclude 'slow', use "database and not slow".

3. Final Answer:

   pytest -m "database and not slow" -> Option B

4. Quick Check:

   Use boolean logic in -m to include/exclude markers [OK]

Hint: Use boolean logic: -m "marker and not other" [OK]

Common Mistakes:

• Using 'or' instead of 'and not' to exclude
• Misplacing 'not' before the first marker
• Combining markers without quotes