Running tests (pytest command) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest with a failing test

What will be the output summary when running pytest on the following test file containing one passing and one failing test?

PyTest

def test_pass():
    assert 1 == 1

def test_fail():
    assert 2 == 3

A 2 passed in 0.01s

B 1 failed in 0.01s

C 1 passed, 1 failed in 0.01s

D No tests collected

💡 Hint

pytest reports the number of tests passed and failed after running.

pytest runs both tests. One passes, one fails, so the summary shows '1 passed, 1 failed'.

❓ assertion

intermediate

Correct assertion to check a function raises an exception

Which pytest assertion correctly tests that calling function foo() raises a ValueError?

PyTest

def foo():
    raise ValueError('error')

A assert foo() == ValueError

B

with pytest.raises(ValueError):
    foo()

C assert foo() raises ValueError

D assert foo() throws ValueError

💡 Hint

pytest has a special context manager for checking exceptions.

pytest.raises is the correct way to assert exceptions in pytest. Other options are invalid syntax or incorrect.

🔧 Debug

advanced

Why does pytest not discover tests in this file?

Given this test file named test_sample.py, pytest does not find any tests. Why?

PyTest

def sample_test():
    assert True

A Test function name does not start with 'test_'

B Function has no parameters

C Missing import pytest statement

D File name should not start with 'test_'

💡 Hint

pytest discovers tests by function name patterns.

pytest only discovers functions starting with 'test_'. 'sample_test' does not match, so no tests found.

❓ framework

advanced

How to run pytest with detailed output and stop after first failure

Which pytest command runs tests showing detailed info and stops after the first failure?

A pytest -q --maxfail=0

B pytest --maxfail=1 --quiet

C pytest --stop-on-failure --verbose

D pytest -v -x

💡 Hint

Check pytest options for verbosity and stopping on failure.

-v is verbose, -x stops after first failure. Other options are invalid or contradictory.

🧠 Conceptual

expert

Understanding pytest fixture scope impact on test runs

If a pytest fixture has scope='module', how many times is it set up and torn down when running 5 tests in the same module?

A Setup once before all 5 tests, teardown once after all tests

B Setup and teardown before and after each test (5 times each)

C Setup and teardown twice, splitting tests into groups

D Setup once before first test, teardown after third test

💡 Hint

Fixture scope controls how often setup/teardown runs.

Module scope means fixture runs once per module, so setup and teardown happen once for all tests in that module.