Docker-based test execution in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pytest run inside Docker container

Consider a Docker container running a pytest suite with the following test file test_sample.py:

def test_addition():
    assert 2 + 3 == 5

def test_subtraction():
    assert 5 - 3 == 1

What will be the result of running pytest inside the container?

PyTest

def test_addition():
    assert 2 + 3 == 5

def test_subtraction():
    assert 5 - 3 == 1

A 2 passed

B 0 tests collected

C 2 failed

D 1 passed, 1 failed

💡 Hint

Check the assertions carefully for correctness.

The first test passes because 2 + 3 equals 5. The second test fails because 5 - 3 equals 2, not 1.

❓ locator

intermediate

Best locator for pytest test file in Docker context

You want to run pytest inside a Docker container. Which file path locator is best to specify the test file test_api.py located in the /app/tests/ directory inside the container?

A ./tests/test_api.py

B /app/tests/test_api.py

C /tests/test_api.py

D tests/test_api.py

💡 Hint

Inside Docker, absolute paths are more reliable if you know the working directory.

Using the absolute path /app/tests/test_api.py ensures pytest finds the test file regardless of the current working directory inside the container.

❓ assertion

advanced

Assertion outcome in Docker pytest log

Inside a Docker container, a pytest test contains:

def test_string():
    result = 'hello'.upper()
    assert result == 'HELLO'

What will be the assertion outcome when running pytest inside Docker?

PyTest

def test_string():
    result = 'hello'.upper()
    assert result == 'HELLO'

A Test raises TypeError

B Test fails with AssertionError

C Test passes

D Test is skipped

💡 Hint

Check the string method and expected value carefully.

The upper() method converts 'hello' to 'HELLO', so the assertion is true and test passes.

🔧 Debug

advanced

Debugging pytest failure inside Docker

A pytest test inside Docker fails with:

FileNotFoundError: [Errno 2] No such file or directory: '/data/input.txt'

What is the most likely cause?

A The file /data/input.txt is missing inside the Docker container

B Docker container has no network access

C The test code has a syntax error

D pytest is not installed in the container

💡 Hint

FileNotFoundError means the file path is invalid or file is missing.

The error indicates the test tries to open a file that does not exist inside the container's filesystem.

❓ framework

expert

Choosing Docker test execution strategy for pytest

You want to run pytest tests inside Docker with these requirements:
- Tests must run in isolated containers
- Test results should be collected on host machine
- Tests should run in parallel

Which Docker strategy best fits these requirements?

A Use Docker Compose to spin up multiple containers running pytest in parallel, mounting a shared volume for test reports

B Run pytest directly on host without Docker for faster execution

C Use a single Docker container running pytest sequentially with no volume mounts

D Run pytest inside Docker but do not collect test reports

💡 Hint

Think about isolation, parallelism, and sharing results between container and host.

Docker Compose can orchestrate multiple containers for parallel test runs. Mounting a shared volume allows test reports to be accessible on the host.