From the introduction of the openpolicyagent.org site: OPA generates policy decisions by evaluating the query input against policies and data. In this post i am going to show you an easy and fast way to test your policies by running OPA in Docker. First, make sure you have already installed Docker and have it running: docker ps Inside your choosen directory, create two files. One called input.json file for your system representation and one file called example.rego for your rego policy rules. Add the following content to your json file: Add the following content for the example.rego: Each violation block represents the rule that you want to validate your system against. The first violation block checks if any of the system servers have the http protocol in it. If that is the case, the server id is added to the array. In the same way, the second violation block checks for the servers that have the telnet protocol in it and if it finds a match the server id is also