Test modules in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest test discovery

Given the following test module, what will pytest report when run?

PyTest

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

def test_subtraction():
    assert 2 - 1 == 1

class TestMath:
    def test_multiply(self):
        assert 2 * 3 == 6

    def helper(self):
        return 5

A 3 passed tests

B 2 passed tests, 1 skipped

C 2 passed tests

D 1 passed test, 2 failed

💡 Hint

pytest discovers functions starting with 'test_' and methods inside classes named 'Test' starting with 'test_'.

pytest will find test_addition, test_subtraction, and test_multiply inside TestMath. The method helper is ignored because it does not start with 'test_'. All three tests pass.

❓ assertion

intermediate

Correct assertion for checking exception in pytest

Which assertion correctly tests that a function raises a ValueError when called with invalid input?

PyTest

def func(x):
    if x < 0:
        raise ValueError("Negative value")
    return x

A assert func(-1) raises ValueError

B assert func(-1) == ValueError

C

with pytest.raises(ValueError):
    func(-1)

D assertRaises(ValueError, func, -1)

💡 Hint

Use pytest's context manager to check exceptions.

Option C uses pytest.raises context manager correctly to check for exceptions. Option C compares return value to exception class, which is incorrect. Option C is invalid syntax. Option C is unittest style, not pytest.

🔧 Debug

advanced

Identify the cause of test not running

Why does pytest not run the test method in this module?

PyTest

class math_tests:
    def test_divide(self):
        assert 10 / 2 == 5

A Class name does not start with 'Test', so pytest ignores it.

B The assert statement is incorrect and causes a syntax error.

C Method name does not start with 'test_', so pytest ignores it.

D The division operator is invalid in Python.

💡 Hint

pytest requires test classes to start with 'Test'.

pytest discovers test classes only if their names start with 'Test'. Here, the class is named 'math_tests' (lowercase 'm'), so pytest ignores it. The method name is correct, and the assert and division are valid.

❓ framework

advanced

Best practice for test module organization

Which option describes the best practice for organizing test modules in a pytest project?

A Write all tests in a single large file named 'all_tests.py'.

B Put all tests inside the main application modules to keep code together.

C Name test files with any name and place them randomly in the project.

D Place test files in a separate 'tests' directory with filenames starting with 'test_'.

💡 Hint

pytest automatically discovers tests in files named 'test_*.py' or '*_test.py'.

Option D follows pytest conventions: tests in a separate 'tests' folder and files named starting with 'test_'. This helps pytest find and run tests easily. Other options reduce clarity and maintainability.

🧠 Conceptual

expert

Understanding pytest fixture scope impact on test modules

Consider a pytest fixture defined with scope='module'. What is the impact of this scope on tests within the same module?

A The fixture is created once for the entire test session and shared globally.

B The fixture is created once per module and shared by all tests in that module.

C The fixture is created once per test class and shared only within that class.

D The fixture is created once per test function and destroyed after each test.

💡 Hint

Fixture scopes control how often the fixture setup runs.

Scope='module' means the fixture runs once when the module starts and is reused by all tests in that module. This improves performance when setup is expensive. Other scopes are 'function', 'class', and 'session'.