Grouping related tests in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of grouped pytest tests with fixtures

Consider the following pytest code with a fixture and two test functions grouped in a class. What will be the output when running pytest on this file?

PyTest

import pytest

@pytest.fixture
 def setup_data():
     return [1, 2, 3]

class TestGroup:
    def test_sum(self, setup_data):
        assert sum(setup_data) == 6

    def test_len(self, setup_data):
        assert len(setup_data) == 3

A Both tests pass successfully.

B Both tests fail due to fixture error.

C test_sum passes, test_len fails.

D test_sum fails, test_len passes.

💡 Hint

Think about what the fixture returns and the assertions in each test.

The fixture 'setup_data' returns a list [1, 2, 3]. The sum is 6 and length is 3, so both assertions are true and tests pass.

❓ assertion

intermediate

Correct assertion to check all items in a grouped test

You have a grouped test that checks if all items in a list are positive. Which assertion correctly verifies this in pytest?

PyTest

def test_all_positive():
    data = [5, 10, 15]
    # Which assertion is correct here?

A assert data > 0

B assert any(x > 0 for x in data)

C assert sum(data) > 0

D assert all(x > 0 for x in data)

💡 Hint

Think about checking every item, not just some or the sum.

Using all() ensures every item is greater than zero, which matches the test goal.

🔧 Debug

advanced

Identify the cause of test skipping in grouped pytest tests

Given this pytest code, why is the test 'test_feature' skipped when running the group?

PyTest

import pytest

@pytest.mark.skipif(True, reason="Feature not ready")
class TestFeatures:
    def test_feature(self):
        assert True

A The test is skipped because the assertion is True.

B The skipif decorator on the class causes all tests inside to be skipped.

C The test is skipped due to a syntax error in the code.

D The test is skipped because pytest cannot find the test function.

💡 Hint

Look at the decorator and its condition.

The @pytest.mark.skipif(True) on the class causes pytest to skip all tests inside unconditionally.

❓ framework

advanced

Best practice for grouping tests in pytest

Which of the following is the best practice to group related tests in pytest for better organization and reuse?

A Group tests inside classes without __init__ and use fixtures for setup.

B Group tests inside classes with __init__ methods to initialize data.

C Write all tests as standalone functions without grouping.

D Use global variables to share data between tests.

💡 Hint

Think about pytest conventions and fixture usage.

Pytest recommends grouping tests in classes without __init__ and using fixtures for setup to keep tests isolated and organized.

🧠 Conceptual

expert

Effect of test grouping on test discovery and execution order in pytest

In pytest, how does grouping tests inside classes affect test discovery and execution order compared to standalone test functions?

A Grouping tests inside classes disables test discovery for those tests.

B Tests inside classes are discovered but run in random order; standalone functions run alphabetically.

C Tests inside classes are discovered and run in the order they appear; standalone functions run in file order.

D Grouping tests inside classes causes tests to run before standalone functions always.

💡 Hint

Consider how pytest collects and orders tests.

Pytest discovers tests in file order. Tests inside classes run in the order they appear in the class, preserving grouping order.

Practice

1. What is the main benefit of grouping related tests in pytest?

easy

A. It keeps the test suite organized and easier to manage

B. It makes tests run faster automatically

C. It removes the need for assertions in tests

D. It prevents tests from running in parallel

Solution

1. Step 1: Understand test grouping purpose

   Grouping tests helps organize them logically by feature or behavior.

2. Step 2: Identify the main benefit

   This organization makes the test suite easier to maintain and understand.

3. Final Answer:

   It keeps the test suite organized and easier to manage -> Option A

4. Quick Check:

   Grouping = Organized tests [OK]

Hint: Grouping means organizing tests for easier management [OK]

Common Mistakes:

• Thinking grouping speeds up tests automatically
• Believing grouping removes need for assertions
• Assuming grouping disables parallel runs

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

easy

A. @pytest.group('fast')\ndef test_example(): pass

B. @pytest.group_mark('fast')\ndef test_example(): pass

C. @pytest.mark.fast\ndef test_example(): pass

D. @pytest.tag('fast')\ndef test_example(): pass

Solution

1. Step 1: Recall pytest syntax for marking tests

   pytest uses @pytest.mark.<groupname> to mark tests for grouping.

2. Step 2: Match correct syntax

   @pytest.mark.fast is the correct decorator to mark a test as 'fast'.

3. Final Answer:

   @pytest.mark.fast\ndef test_example(): pass -> Option C

4. Quick Check:

   Use @pytest.mark.groupname for grouping [OK]

Hint: Use @pytest.mark.groupname to mark tests [OK]

Common Mistakes:

• Using @pytest.group instead of @pytest.mark
• Using @pytest.tag which does not exist
• Incorrect decorator names like @pytest.group_mark

3. Given the following pytest code, what tests will run when executing pytest -m "slow"?

import pytest

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

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

class TestGroup:
    @pytest.mark.slow
    def test_c(self):
        assert True

    def test_d(self):
        assert True

medium

A. test_a and test_c only

B. test_b and test_d only

C. All tests test_a, test_b, test_c, test_d

D. Only test_c

Solution

1. Step 1: Understand pytest -m option

   The -m option runs tests marked with the given marker, here 'slow'.

2. Step 2: Identify tests marked 'slow'

   test_a and test_c have @pytest.mark.slow, so they run. test_b and test_d do not.

3. Final Answer:

   test_a and test_c only -> Option A

4. Quick Check:

   -m "slow" runs tests marked slow [OK]

Hint: -m runs only tests with the matching mark [OK]

Common Mistakes:

• Running all tests ignoring marks
• Including unmarked tests in filtered run
• Confusing class-level marks with method marks

4. What is wrong with this pytest code if the goal is to group tests inside a class named TestMath?

class TestMath:
    def test_add():
        assert 1 + 1 == 2

    def test_subtract(self):
        assert 2 - 1 == 1

medium

A. test_subtract should not have self parameter

B. Class name should not start with Test

C. Tests inside classes cannot have assertions

D. test_add is missing the self parameter

Solution

1. Step 1: Check method definitions inside test classes

   Instance methods inside test classes must have self as first parameter.

2. Step 2: Identify the error

   test_add is missing self, so pytest will error or skip it.

3. Final Answer:

   test_add is missing the self parameter -> Option D

4. Quick Check:

   Test methods in classes need self [OK]

Hint: Test methods in classes must include self parameter [OK]

Common Mistakes:

• Omitting self in test methods
• Thinking class names cannot start with Test
• Removing assertions from test methods

5. You want to run only tests related to the login feature in your pytest suite. You have marked tests with @pytest.mark.login and grouped some inside a class TestLogin. Which command will correctly run all login tests, including those inside the class?

hard

A. pytest -k login

B. pytest -m login

C. pytest --group=login

D. pytest --run-login

Solution

1. Step 1: Understand pytest options for running grouped tests

   pytest uses -m to run tests marked with a specific marker like 'login'.

2. Step 2: Identify correct command

   pytest -m login runs all tests marked with @pytest.mark.login, including those inside classes.

3. Final Answer:

   pytest -m login -> Option B

4. Quick Check:

   -m runs marked tests, -k filters by test name [OK]

Hint: Use -m with marker name to run grouped tests [OK]

Common Mistakes:

• Using -k which filters by test name, not marker
• Using nonexistent options like --group or --run-login
• Assuming class name filters tests automatically