Often when you want to run some tests you need to install required dependencies such as python packages, ruby gems, npm packages and so on. Nowadays tests are executed automatically for pull (merge) requests in various CI systems. Dependency pulling is repeated again and again for every test run and it takes time. We cannot do much about it in cloud based CI systems such as Travis, Circle CI or Github Actions but there is some space for improvement for self-hosted Gitlab CI, Jenkins and others.