I've recently created a video about how to use the so called 'standalone container' for rapid deployment and testing of plugins.
The standalone container itself is nothing but a tiny wrapper around the standard plugin-container in the agent. So by using the standalone container, you can deploy the plugins in a plugin container without the need to start a full blown RHQ server/agent setup.
Last week I was talking at the HfT Stuttgart to students and had them as exercise also writing a simple plugin and testing it in the standalone container. And while it was the most natural for me that I would know the names of operations or metrics, one of the students came up with the idea to add a command to list the allowed operations of a resource. So master has now the options to pass a '-list' parameter to invoke and measure commands to list the operations and metrics available.