One annoying problem I encountered while testing AWS CDK Constructs using pytest

Module not found error

AWS has released the “assertions” library to test the cloud formation template generated from CDK. This blog post covers one annoying problem I encountered using pytest when I want to run tests and deploy using an AzureDevops multi-stage pipeline.

more information can be found at this official link https://docs.aws.amazon.com/cdk/v2/guide/testing.html

I kept all my test files in a separate test folder and ran tests on that particular folder using the below command from a pipeline.

cd <test directory>: python -m pytest or pytest /

I kept all the other stack files in the root directory. I used the below command to deploy my stacks to AWS cloud

cd <root directory/projects/my_project>: cdk deploy

Problem:

Pytest wants me to specify the imports with an absolute path, if not I will get Module not found error

Pytest wants like: from rootdirectory.projects.my_project.file import func

whereas CDK does not want me to specify the absolute path, if I specify I will get Module not found error.

CDK wants like: from file import func

Solution:

We need to tell the virtual environment about the folder structure in the project.

After the virtual environment is activated, we need to specify the PYTHONPATH value. In my case, I was using a bash task inside Azure DevOps so I have to specify

export PYTHONPATH=”${PYTHONPATH}:$(System.DefaultWorkingDirectory)”

Now I have informed pytest and cdk about my folder structure so I can specify from rootdirectory.projects.my_project.file import func

which is working for both the tests and deployment from the multi-stage pipeline.