The project is more or less defunct, so don't bother.
The 'rbx-head' ruby is not valid, although the documentation says it is.
The Guard configuration runs specs and features with debugger support (specs only) and with progress-style output omitting exception backtraces. The 'test' Rake tasks run specs and features without debugger support and with progress-style output, including a backtrace when exceptions occur. The `rake test` command is invoked by `gem test` also in Travis CI builds. The 'spec' and 'features' Rake tasks run specs and features with debugger support (specs only) and with documentation-style output omitting exception backtraces. The `spec` and `cucumber` commands run specs and features with debugger support (specs only) and with documentation-style output omitting exception backtraces.
The readme implies you can mirror all Rake tasks in a standard Rails project by simply calling Cape.mirror_rake_tasks with no arguments. Capistrano raises ArgumentError when you try to define a task whose name collides with a Ruby method name. For example a 'load' Rake task collides with the core method Kernel#load when you try to mirror it as a Capistrano recipe. There are Rake tasks defined by Rails that have the same problem. Instead of bubbling the error from Capistrano, we are writing a warning to stderr and ignoring the offending task.
Beginning in v10.1, Rake removes the trailing period of task descriptions. In Cucumber features, rather than sniff the Rake version and assert on Cape's behavior that adds a trailing period if necessary, we're doing away with the broken assertions which cover hardly-critical functionality.