How to speed up mysql docker container for tests?

I use docker/docker-compose to run services and tests. One of the services is mysql:

db:
    image: mysql:5.6
    environment:
      - MYSQL_ALLOW_EMPTY_PASSWORD=yes
    expose:
      - "3306"

It takes quite some time to start the MySQL service and run database-related operations. Is there any way I can tune the container specifically for tests and speed (e.g. keep everything in memory, etc.).