How Dockerized Testing Solved Our Pytest Configuration Duplication Issue in a Monorepo

Mar 26, 2025 | docker, pytest, monorepo, testing

Managing test configurations in a monorepo can be challenging, especially when dealing with multiple microservices. Each service often requires its own test setup, which can lead to redundant code and maintenance headaches. In this post, we’ll discuss how we tackled this issue by leveraging Docker to centralize and streamline our pytest configuration, reducing duplication and improving maintainability.

Brief

In our project, which follows a microservices architecture and is maintained in a monorepo, we encountered a significant challenge with test configuration duplication. Each microservice is a distinct FastAPI application, and we use pytest for testing.

The Problem: Code Duplication in Pytest Configuration

Pytest generally expects test files inside a folder named tests/, and it allows defining shared test configurations in a conftest.py file within the same directory. Since each microservice had its own test directory (tests/), we initially placed a separate copy of conftest.py inside each service’s tests/ folder.

While this approach worked functionally, it led to a code duplication issue when we pushed our code to the main branch. SonarQube flagged a 37% duplication rate, primarily because the conftest.py file was identical across multiple services.

The Solution: Dockerized Testing

To eliminate redundancy, we decided to maintain a single instance of conftest.py at the root of our monorepo (snake-charmers/). However, pytest still required conftest.py inside each service’s tests/ folder for test execution.

How Docker Helped

Instead of manually copying conftest.py across services, we leveraged Docker’s build process:

• During image build, we copied conftest.py into each service’s tests/ folder inside the container.
  

• This ensured that each service had its own conftest.py inside the container while avoiding duplication in the codebase.