Running tests in containers in Docker - Mini Project: Build & Apply

Running Tests in Containers

📖 Scenario: You are working on a small Python project. You want to run your tests inside a Docker container to make sure they work the same way on any computer.

🎯 Goal: Build a Docker setup that runs Python tests inside a container using docker run.

📋 What You'll Learn

Create a Dockerfile that uses the official Python 3.12 image

Copy the test script into the container

Set a command to run the test script

Run the container and see the test output

💡 Why This Matters

🌍 Real World

Running tests inside containers ensures your code works the same on any machine, avoiding the 'it works on my computer' problem.

💼 Career

Many companies use containers to run tests in continuous integration pipelines, so knowing this helps you work in modern DevOps environments.

1

Create a simple Python test script

Create a file named test_script.py with a Python test function called test_addition that checks if 2 + 2 equals 4 and prints Test passed if true.

Docker

# Create test_script.py with test_addition function
# Your code here

Need a hint?

Write a function named test_addition that prints Test passed if 2 + 2 equals 4.

2

Write a Dockerfile to run the test script

Create a Dockerfile that uses the base image python:3.12-slim, copies test_script.py into the container, and sets the default command to run python test_script.py.

Docker

def test_addition():
    if 2 + 2 == 4:
        print("Test passed")

if __name__ == "__main__":
    test_addition()

# Create Dockerfile below
# Your code here

Need a hint?

Use FROM python:3.12-slim and copy the test script to /app. Set CMD to run the script.

3

Build the Docker image

Write the exact docker build command to build an image named test-runner from the current directory.

Docker

def test_addition():
    if 2 + 2 == 4:
        print("Test passed")

if __name__ == "__main__":
    test_addition()

# Dockerfile content
FROM python:3.12-slim
COPY test_script.py /app/test_script.py
WORKDIR /app
CMD ["python", "test_script.py"]

# Write docker build command below
# Your code here

Need a hint?

Use docker build -t test-runner . to build the image.

4

Run the container to execute the tests

Write the exact docker run command to run the test-runner image and show the test output.

Docker

def test_addition():
    if 2 + 2 == 4:
        print("Test passed")

if __name__ == "__main__":
    test_addition()

# Dockerfile content
FROM python:3.12-slim
COPY test_script.py /app/test_script.py
WORKDIR /app
CMD ["python", "test_script.py"]

docker build -t test-runner .

# Write docker run command below
# Your code here

Need a hint?

Use docker run --rm test-runner to run the container and see the output.