Wordpress
Planet 4 is built on top of Wordpress, so it's important to keep an eye on what's coming in future releases. To avoid any surprises we use a CI environmental variable (WP_VERSION) to set the Wordpress version for all instances. When a new release comes out, we first check its Changelog for any breaking change before we bump that version variable for Planet 4.
To make sure new PR tests and our local environment also are in the same WP version we explicitly have WP_VERSION variable in config.yml and docker-compose*.yml files at the app repos and docker-compose respectively.
If we need to test a different version (eg. when a new release comes out) we can override that global variable for a specific instance. To do so we just need to add a WP_VERSION in the environment variables of this instance CirclecI config. Example:
job_environments:common_environment: &common_environment​WP_VERSION: 5.4
