Caddis: The On-The-Fly JSON RESTful Server

2014 February 18th by todd anderson

Recently I released a new node-based CLI tool called caddis. It allows you to start a server - as a daemon - on localhost and dynamically add routes and JSON responses. Once stopped, any work is wiped; it is purely in-memory, session based.

The impetus for its creation was a requirement to easily mock service APIs to be called in a test environment without regards to libraries or languages in which the environment is run.

To be more specific, for a recent project I am using the wonderful calabash-ios framework to define cucumber specs in Ruby that drive automated integration tests for an iOS project in the simulator. Creating caddis allows me to easily mock service requests that the iOS application will make and validate the expected result of scenarios in cucumber.

Installation & Usage

caddis is available through npm. It is recommended that you install globally:

$ npm install -g caddis

> you may need to sudo

To use caddis

$ caddis start
$ curl -X POST -d '{"method":"GET", "uri":"/foo", "response":{"bar":"baz"}}' http://localhost:3001/api --header "Content-Type:application/json"

Visit http://localhost:3001/foo, prints:

  bar: 'baz'
$ caddis stop

Visit http://localhost:3001/foo, Not Found.


$ caddis -h

usage: caddis [action]

Starts a server at http://localhost:3001 as a daemon, exposing an api to post JSON to in order to mock a RESTful service.

  start               Start Caddis at http://localhost:3001
  stop                Stop a previously started Caddis daemon
  -h                  Display this help menu


Caddis Fly Lure
A caddis is a moth-like insect often used as models for fly lures in fishing.

The caddis CLI tool is used to start and stop a RESTful JSON service with the ability to POST route configuration and responses, on-the-fly, for mocking and testing purposes.

It may be a stretch, but there's wit in there somewhere...


There are other projects I have been a part of, such as madmin, that allow for dynamically creating RESTful APIs through a User Interface and allows for persistance through I/O.

Recently, I was involved with mocking a service layer for unit testing purposes and found that the manual curation of such an API was too tedious for the task at hand - I wanted the process to be much more fluid and simple.

In this particular instance I needed to:

  1. Start a server in setup/before
  2. Dynamically add a route to the service with mock JSON response
  3. Run the test
  4. Shut down the server in teardown/after

Fairly simple, and most of all I didnt want any artifacts lying around - in other words I didn't need for any routes that I dynamically created to stick around on my local disk after the tests were done.

As such, caddis was born.


As mentioned briefly above, caddis is a CLI tool. It is recommended to install globally:

$ npm install -g caddis

> you may need to sudo

Once installed, you can start the service (currently defaults to http://localhost:3001) and begin POSTing route configurations in JSON. Here is an example using cUrl that dynamically adds a GET route at /foo with a simple JSON payload of {"bar":"baz"}:

$ curl -X POST -d '{"method":"GET", "uri":"/foo", "response":{"bar":"baz"}}' http://localhost:3001/api --header "Content-Type:application/json"

You are not confiuned to cUrl - you can use whatever networking library in whatever language you are writing your tests in and the server can handle all modern RESTful methods:

  • GET
  • POST
  • PUT

When you are finished, simply stop the caddis server:

$ caddis stop


I hope this was a useful introduction to what caddis has to offer and that you may find it beneficial in your testing in some way.

You can visit the project on github at: