><code>default_command</code> can be used to specify the command to run if none is given. <code>bin/test</code> uses this to run <code>bin/test run</code>.</li><li><code>requires_project_env</code> can be used at the app or command level to indicate that <code>--env</code> is accepted on the command line to set the project environment for the code to run in. Omitting this means that the actual project env used when the app runs is undefined.</li><li>Use <code>env_var</code> to document environment variables