Running tests by marker (-m) in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest run with marker filter

Given the following pytest test file, what tests will run when executing pytest -m "slow"?

PyTest

import pytest

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

@pytest.mark.fast
def test_b():
    assert True

def test_c():
    assert True

A All tests run

B test_a and test_b run

C test_b and test_c run

D Only test_a runs

💡 Hint

The -m option runs tests matching the given marker expression.

The command pytest -m "slow" runs only tests marked with @pytest.mark.slow. Here, only test_a has that marker.

❓ assertion

intermediate

Correct assertion for marker presence in pytest

Which assertion correctly checks that a test function is marked with the marker 'database' in pytest?

PyTest

import pytest

@pytest.mark.database
def test_query():
    pass

A assert any(marker.name == 'database' for marker in test_query.pytestmark)

B assert 'database' in test_query.__pytest_markers__

C assert 'database' in test_query.pytestmark

D assert test_query.has_marker('database')

💡 Hint

pytest stores markers as objects in the pytestmark attribute list.

pytest marks are stored as objects in the list test_query.pytestmark. We must check if any marker's name equals 'database'.

🔧 Debug

advanced

Why does pytest -m 'api and not slow' run no tests?

Given these tests:

import pytest

@pytest.mark.api
@pytest.mark.slow
def test_api_slow():
    pass

@pytest.mark.api
def test_api_fast():
    pass

@pytest.mark.slow
def test_slow():
    pass

Why does pytest -m "api and not slow" run no tests?

A Because the expression excludes all tests marked both api and slow, but test_api_fast is only api so it should run

B Because 'not' is not a valid operator in pytest marker expressions

C Because pytest marker expressions require quotes around 'not'

D Because test_api_fast is not marked slow, so it should run but does not due to syntax error

💡 Hint

Check pytest documentation for valid marker expression operators.

pytest marker expressions support 'and', 'or', but not 'not'. Using 'not' causes no tests to run.

❓ framework

advanced

How to run tests marked 'ui' or 'integration' but not 'slow' in pytest

Which pytest command runs tests marked with 'ui' or 'integration' but excludes those marked 'slow'?

A pytest -m "(ui or integration) and not slow"

B pytest -m "ui or integration and slow"

C pytest -m "ui or integration and not slow"

D pytest -m "ui or integration and not slow" --disable-warnings

💡 Hint

Remember operator precedence and valid operators in pytest marker expressions.

pytest supports 'and' and 'or' but not 'not'. The correct expression is without parentheses and uses 'and' and 'or'.

🧠 Conceptual

expert

Understanding pytest marker expression evaluation order

In pytest marker expressions, which operator has higher precedence?

A 'and' has higher precedence than 'or'

B 'or' has higher precedence than 'and'

C 'and' and 'or' have equal precedence and are evaluated left to right

D Precedence depends on the pytest version and is unpredictable

💡 Hint

Think about how logical operators usually work in programming languages.

In pytest marker expressions, 'and' has higher precedence than 'or', similar to Python logical operators.