Adding docs for testing with Docker

.vuepress/config-en.js

@@ -114,7 +114,8 @@ module.exports = {
                     'framework/mocking',
                     'framework/support-classes',
                     'framework/full-mock',
-                    'framework/assertion-helpers'
+                    'framework/assertion-helpers',
+                    'framework/docker',
                 ]
             },
 

testing/framework/docker.md

@@ -0,0 +1,31 @@
+# Testing with Docker
+
+To make things easier, Craft ships with a `docker-compose.yaml` file in the tests directory. This is useful when you
+need to run tests against Craft supported databases.
+
+Instead of installing PostgreSQL and MySQL/MariaDB on your machine, you can use the `docker-compose.yaml` file to
+scaffold the databases.
+
+## Ports
+
+The Docker Compose file that ships with Craft is configured with PostgreSQL and MySQL on the following ports:
+
+| Database | Port |
+| ----------- | ----------- |
+| PostgreSQL | 5432 |
+| MySQL | 3306 |
+| MariaDB | 33061 |
+
+::: tip
+If these ports conflict with an existing install, you can update the port on the `docker-compose.yaml` file to look like
+this:
+
+```yaml
+mysql:
+  image: mysql:5.6
+  ports:
+    - 33060:3306
+```
+
+The port on the left side of the colon is your physical machine port and can be changed at will (remember to update your .env to use the new port).
+:::