Why organized tests scale with projects in PyTest - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple test function using pytest.

PyTest

def test_addition():
    assert 2 + 2 == [1]

Drag options to blanks, or click blank then click option'

A5

B3

C22

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Using 5 or 3 instead of 4 will cause the test to fail.

Writing the number as a string like '4' instead of 4.

The test checks if 2 + 2 equals 4, which is true. This simple assertion helps verify basic functionality.

2fill in blank

medium

Complete the code to mark a test as expected to fail using pytest.

PyTest

import pytest

@pytest.mark.[1]()
def test_fail_example():
    assert False

Drag options to blanks, or click blank then click option'

Askip

Bxfail

Cparametrize

Dfixture

Attempts:

3 left

💡 Hint

Common Mistakes

Using @pytest.skip will skip the test instead of marking it as expected fail.

Using @pytest.fixture or @pytest.parametrize are unrelated to expected failure.

The decorator @pytest.mark.xfail() marks the test as expected to fail, so pytest reports it differently without failing the whole suite.

3fill in blank

hard

Fix the error in the test function to correctly check if a list is empty.

PyTest

def test_empty_list():
    my_list = []
    assert [1] == 0

Drag options to blanks, or click blank then click option'

Alen(my_list)

Bmy_list.length

Cmy_list[0]

Dmy_list

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to access my_list[0] causes an error if the list is empty.

Using my_list.length is invalid in Python.

Using len(my_list) returns the number of items in the list, which should be 0 if empty. Checking my_list directly won't compare to 0.

4fill in blank

hard

Fill both blanks to create a test that checks if a string contains a substring.

PyTest

def test_substring():
    text = "hello world"
    assert [1] in [2]

Drag options to blanks, or click blank then click option'

A"world"

B"hello"

Ctext

D"planet"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of substring and string will cause the test to fail.

Using a substring not present in the string will fail the test.

The test checks if the substring "world" is inside the string variable text. This is a common way to verify content in strings.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that filters words longer than 3 characters.

PyTest

words = ["cat", "house", "dog", "elephant"]
lengths = { [1]: [2] for [3] in words if len([3]) > 3 }

Drag options to blanks, or click blank then click option'

Aword

Blen(word)

D{

Attempts:

3 left

💡 Hint

Common Mistakes

Not starting with a curly brace causes syntax errors.

Swapping key and value will produce incorrect dictionaries.

Using a variable name not defined in the loop causes errors.

The dictionary comprehension syntax starts with a curly brace {. It maps each word to its length len(word) for words longer than 3 characters.

Practice

1. Why is it important to organize tests into folders and files in a pytest project?

easy

A. It automatically fixes bugs in the code.

B. It makes tests run faster by using less memory.

C. It helps find and run tests quickly as the project grows.

D. It hides tests from other team members.

Solution

1. Step 1: Understand test organization purpose

   Organizing tests into folders and files groups related tests logically.

2. Step 2: Recognize benefits for large projects

   This grouping makes it easier to find and run specific tests quickly as the project grows.

3. Final Answer:

   It helps find and run tests quickly as the project grows. -> Option C

4. Quick Check:

   Organized tests = easier management [OK]

Hint: Organize tests to find them fast in big projects [OK]

Common Mistakes:

• Thinking organization speeds up test execution
• Believing organization fixes code bugs automatically
• Assuming organization hides tests from teammates

2. Which of the following is the correct way to name a pytest test file?

easy

A. TestExample.py

B. exampletest.py

C. example.py

D. test_example.py

Solution

1. Step 1: Recall pytest naming conventions

   Pytest requires test files to start with 'test_' or end with '_test.py'.

2. Step 2: Check options against convention

   Only 'test_example.py' starts with 'test_' and follows lowercase naming.

3. Final Answer:

   test_example.py -> Option D

4. Quick Check:

   File name starts with 'test_' [OK]

Hint: Test files start with 'test_' prefix [OK]

Common Mistakes:

• Using uppercase letters in test file names
• Not starting file name with 'test_'
• Naming files without 'test' keyword

3. Given this pytest folder structure:

tests/
  test_math.py
  test_strings.py
  utils/
    test_helpers.py

Which command runs all tests inside the utils folder?

medium

A. pytest tests/utils

B. pytest tests/test_helpers.py

C. pytest tests/test_strings.py

D. pytest utils

Solution

1. Step 1: Understand folder structure and test locations

   Tests inside 'utils' folder are under 'tests/utils'.

2. Step 2: Identify correct pytest command to run folder tests

   Running 'pytest tests/utils' runs all tests in that folder.

3. Final Answer:

   pytest tests/utils -> Option A

4. Quick Check:

   Run tests by folder path [OK]

Hint: Run tests by specifying folder path [OK]

Common Mistakes:

• Running tests with wrong folder path
• Trying to run tests without 'tests/' prefix
• Running unrelated test files

4. You have this test file named test_calc.py but pytest does not discover any tests inside it. What is the most likely reason?

medium

A. The file name should be calc_test.py

B. Test functions inside do not start with 'test_'

C. Pytest requires tests to be in the root folder only

D. The file is missing a main function

Solution

1. Step 1: Recall pytest test discovery rules

   Pytest finds test functions only if their names start with 'test_'.

2. Step 2: Identify why tests are not found

   If functions inside 'test_calc.py' don't start with 'test_', pytest ignores them.

3. Final Answer:

   Test functions inside do not start with 'test_' -> Option B

4. Quick Check:

   Function names must start with 'test_' [OK]

Hint: Test functions must start with 'test_' [OK]

Common Mistakes:

• Renaming test files incorrectly
• Thinking pytest needs a main function
• Assuming tests must be in root folder

5. In a large pytest project, how does grouping tests by feature folders help a team work better together?

hard

A. It allows team members to work on different features without conflicts.

B. It makes tests run in parallel automatically without setup.

C. It forces all tests to run every time, ensuring full coverage.

D. It hides test failures from other team members.

Solution

1. Step 1: Understand test grouping by feature

   Grouping tests by feature means tests for one feature are in one folder.

2. Step 2: Recognize team collaboration benefits

   This lets team members work on separate features and tests without interfering with each other.

3. Final Answer:

   It allows team members to work on different features without conflicts. -> Option A

4. Quick Check:

   Feature folders = smooth teamwork [OK]

Hint: Group tests by feature for smooth teamwork [OK]

Common Mistakes:

• Thinking grouping runs tests in parallel automatically
• Believing grouping forces all tests to run every time
• Assuming grouping hides test failures