Writing your own plugins

Most uses of RoboHydra need writing custom plugins for the behaviour you want. Writing plugins is easy, as you can use ready-made RoboHydra heads that do most common operations. See the tutorial to get an idea of what’s possible and get started, and the head documentation for a detailed description of the capabilities of each type of head.

A plugin is a directory-based Node package (ie. you can’t have plugins like robohydra/plugins/my-plugin.js, it has to be robohydra/plugins/my-plugin/index.js or similar) that defines the function getBodyParts, and maybe also the function getSummonerTraits. When loading your plugin, RoboHydra will call getBodyParts with two parameters:

  • conf: this is a Javascript object with all configuration properties defined in the configuration file and/or the command-line, plus the special configuration keys robohydra (the RoboHydra object loading the plugin) and path (the full path to the plugin directory, although it’s also available as __dirname under Node).
  • modules: this is a Javascript object with special modules for the plugin to use. Currently there are two modules available: assert, used for assertions (see “The ‘assert’ module” below); and fixtures, used to load fixtures (see “The ‘fixtures’ module” below).

The getBodyParts function must return an object with the following optional properties:

  • heads: an array of RoboHydraHead objects.
  • scenarios: an object with scenario names as properties, and objects as values.

For more information about how to define heads read the “RoboHydra heads” section. For more information about the getSummonerTraits function read the “RoboHydra summoners” section. For more information about scenarios read the “Defining Scenarios” section.


Modules are utility functions available to plugins via the second parameter to getBodyParts. This parameter is an object with several keys (assert, fixtures, …), defined below:

The “assert” module

The assert module defines all functions in Node’s assert module. However, there are two key differences between RoboHydra’s assert module and Node’s:

  1. RoboHydra’s assert functions are tied to the RoboHydra server, allowing RoboHydra to fetch and store the results and present them on the web interface.

  2. RoboHydra’s assert functions won’t die when there’s an assert failure, but instead will return false. This is much more useful because it allows you to easily return a normal response to the client (the same or different than the response the client would get if the assertion had passed).

These functions are used like modules.assert.equal(actual, expected).

The “fixtures” module

The fixtures module defines a single function, load, to load fixtures. Fixtures are files inside the fixtures/ subdirectory inside a plugin directory. From the plugin code you can call modules.fixtures.load("foo.bar") to load the file <plugindir>/fixtures/foo.bar. Note that it returns a Buffer object (not a string!) or throw an exception if the fixture is not found or not readable.


See the example plugins and the standard plugin library in the repository for code examples. Read also about the plugin standard library if you want to avoid implementing already available plugins.

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