Fixture scope (function, class, module, session) in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest fixture with function scope

What will be the output count of the fixture usage in the following pytest code?

PyTest

import pytest

count = 0

@pytest.fixture(scope='function')
def my_fixture():
    global count
    count += 1
    return count

def test_one(my_fixture):
    assert my_fixture == 1

def test_two(my_fixture):
    assert my_fixture == 2

A Both tests fail due to fixture scope error

B Both tests pass; count remains 1

C First test passes; second test fails due to count being 1

D Both tests pass; count increments to 2

💡 Hint

Function scope means fixture runs fresh for each test function.

With function scope, the fixture runs separately for each test function, so count increments each time. The first test gets count=1, the second gets count=2.

❓ Predict Output

intermediate

Effect of class scope on fixture invocation count

Given this pytest code, what is the value of count after running all tests?

PyTest

import pytest

count = 0

@pytest.fixture(scope='class')
def my_fixture():
    global count
    count += 1
    return count

class TestClass:
    def test_one(self, my_fixture):
        assert my_fixture == 1

    def test_two(self, my_fixture):
        assert my_fixture == 1

A count is 1 after tests run

B Tests fail due to fixture scope mismatch

C count is 2 after tests run

D count is 0 after tests run

💡 Hint

Class scope means fixture runs once per test class.

With class scope, the fixture runs once for the entire TestClass, so count increments only once. Both tests get the same fixture value 1.

❓ assertion

advanced

Correct assertion for module scoped fixture reuse

Which assertion correctly verifies that a module scoped fixture is reused across multiple test functions?

PyTest

import pytest

@pytest.fixture(scope='module')
def resource():
    return []

def test_append_one(resource):
    resource.append(1)
    # What assertion here?

def test_append_two(resource):
    resource.append(2)
    # What assertion here?

A assert resource == [1] in test_append_one and [1, 2] in test_append_two

B assert resource == [1] in test_append_one and [2] in test_append_two

C assert resource == [1] in test_append_one and resource == [1, 2] in test_append_two

D assert resource == [1] in test_append_one and resource == [2] in test_append_two

💡 Hint

Module scope means the same fixture instance is shared across tests in the module.

The module scoped fixture returns the same list instance for both tests. After first test, list is [1]. After second test, list is [1, 2]. So assertions must reflect that.

🔧 Debug

advanced

Debugging session scoped fixture with side effects

Why does this session scoped fixture cause tests to fail intermittently?

PyTest

import pytest

@pytest.fixture(scope='session')
def db_connection():
    conn = open_db_connection()
    yield conn
    conn.close()

def test_query_one(db_connection):
    assert db_connection.query('SELECT 1') == 1

def test_query_two(db_connection):
    assert db_connection.query('SELECT 2') == 2

A The fixture is recreated for each test, causing conflicts.

B The fixture closes the connection after the first test, so second test uses closed connection.

C The fixture scope should be 'function' to avoid sharing.

D The fixture does not yield the connection properly, causing NoneType errors.

💡 Hint

Session scope means fixture runs once per test session, but teardown happens after all tests.

The fixture yields the connection once per session, but if the connection is closed too early (e.g., after first test), subsequent tests fail. Proper use of yield ensures teardown after all tests.

🧠 Conceptual

expert

Choosing fixture scope for expensive setup with multiple test classes

You have an expensive setup step needed for multiple test classes in a module. You want to run it only once per module but ensure each test class gets a fresh state derived from that setup. Which fixture scope strategy is best?

A Use a module scoped fixture for the expensive setup, then a class scoped fixture that depends on it to provide fresh state per class.

B Use a session scoped fixture for the setup and share the same state across all classes.

C Use function scoped fixtures only to ensure fresh state for every test.

D Use class scoped fixture for setup and module scoped fixture for state to optimize reuse.

💡 Hint

Think about separating expensive setup from per-class state initialization.

A module scoped fixture runs once for the expensive setup. A class scoped fixture can depend on it and create fresh state for each test class, balancing efficiency and isolation.