Canned fake API server

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Working with APIs, more often than not, during development you want to work with a fixed version of the responses provided. This is especially true if the API is still under development, and maybe even still needs input on how to output something. This is what Canned is for!

What does it do?

Canned maps a folder structure to API responses. Given the following directory structure:


requests like

Accept: application/json
GET /comment/:id

are served from the file /comment/any.get.json as

Content-Type: application/json
{ "content": "I am a comment", "author": "sideshowcoder" }

requests like

Accept: text/html
GET /content/

are served from the file /content/index.get.html as

Content-Type: text/html
  <body>Some html in here</body>

requests like

Accept: application/json
GET /comment/1/votes

are served from the file /comment/1/index.get.json as

Content-Type: application/json
{ "content": "I am comment 1", "author": "sideshowcoder" }

requests like

Accept: application/json
GET /comment/123456789/votes

are served from the file /comment/any/index.get.json

Content-Type: application/json
{ "content": "I am a wildcard comment for any id", "author": "sideshowcoder" }

The matching works on the filename by treating it as PATH.VERB.CONTENT_TYPE so index.get.json has the path index the verb is get and the content-type json. Supported content types are

json   => application/json
html   => text/html
txt    => text/plain
js     => application/javascript
csv    => text/csv
// linked-data formats:
nt     => application/n-triples
jsonld => application/ld+json

So an example is for querying (with canned running on localhost:3000)

$ curl -H "Accept: text/javascript" http://localhost:3000/comment/1
> { "content": "I am a comment", "author": "sideshowcoder" }

Awesome! so what is supported?

Currently Canned supports the basic REST-API mapping, as well as custom method mapping with nested endpoints.

file                            | resquest
/index.get.json                 | GET /
/any.get.json                   | GET /:id
/_search.get.json               | GET /search
/comments/index.get.json        | GET /comments/
/comments/any.get.json          | GET /comments/:id
/comments/_search.get.json      | GET /comments/search
/comments/any/index.get.json    | GET /comments/:id/

You can even add query parameters to your filenames to return different responses on the same route. If the all query params in a filename match the incoming request, this file will be returned. It will fall back to returning the file with no query params if it exists.

Warning this will be deprecated in the future since canned now supports multiple response based on the request body or GET URL parameters in one file. This is the preferred way since files with ? in the name do not work on Windows

file                            | resquest
/index?name=Superman.get.json   | GET /?name=Superman&NotAllParams=NeedToMatch
/_search?q=hello.get.json       | GET /comments/search?q=hello
/_search.get.json               | GET /comments/search?iam=soignored

Same support is available for PUT, POST, etc.

/            | POST serves /... + CORS Headers
/index.put.json             | PUT serves /... + CORS Headers

If CORS support is enabled additionally options will be available as a http verb and all requests will serve the CORS Headers as well

/                           | OPTIONS serve all the options needed for CORS
/index.get.json             | GET serves /... + CORS Headers

If you need some custum return codes, just add them to the file via adding a file header like so

//! statusCode: 201
  <body>Created something successfully! Happy!</body>

The header will be stripped before sending and the statusCode will be set.

You can also override the default content types by adding a custom content type to the file header:

//! contentType: "application/vnd.custom+xml"

This will be returned with a Content-type: application/vnd.custom+xml header.

Multiple headers need to be written on one single line and comma-separated, like so:

//! statusCode: 201, contentType: "application/vnd.custom+xml"

If you need to send bind custom HTTP headers to the response you can add them as headers to the response file using the keyword customHeader:

//! customHeader: {"MyCustomHeaderName": "MyCustomHeaderValue"}

In case you need more then one custom header in the response, you can just use the same keyword multiple times:

//! customHeader: {"MyCustomHeaderName": "MyCustomHeaderValue"}
//! customHeader: {"SecondHeaderName": "SecondHeaderValue"}

Variable responses

You can get a different response by specifying request data in variant comments. If the request data matches the comment data the matching response is returned. If there is no match the first response is returned

Note: comments must be on a single line

Custom headers:

//! header: {"authorization": "abc"}
    "response": "response for abc"

//! header: {"authorization": "123"}
    "response": "response for 123"

If you need different responses based on request body then you can specify the request you want matched via body comments:

//! body: {"email": ""}
    "response": "response for"

//! body: {"email": ""}
    "response": "response for"

If you need different responses based on request parameters then you can specify them via parameters comments:

//! params: {"foo": "bar"}
    "response": "response for bar"

//! params: {"foo": "baz"}
    "response": "response for baz"

this would match http://my.local.server/my_get_request_path?foo=bar or http://my.local.server/my_get_request_path?foo=baz respectively.

To use in conjunction with response headers and status codes, just add them on the line above.

//! statusCode: 201
//! header: {"authorization": "abc"}
    "response": "response for abc"
//! statusCode: 201, contentType: “application/my-personal-json”
//! header: {"authorization": "123"}
    "response": "response for 123"

Wildcard responses are also supported, very useful to have ‘wildcard’ directories, so that if for given a request like:

GET /api/users/1/profile/

you don’t have a file in ./canned/api/users/1/profile/index.get.json then it would look for a file in ./canned/api/users/any/index.get.json or similar. Wildcards can be specified on the command line via

canned –wildcard myany

This would change the lookup to ./canned/api/users/myany/index.get.json

How about some docs inside for the responses?

Most content types support comments natively, like html or javascript. Sadly the probably most used type (JSON) does not :(. So canned actually extends the JSON syntax a little so it can include comments with // or /**/. In case you use the JSON files directly on the backend side as test cases make sure you strip those out as well!

Ok I need this!

Just install via npm

$ npm install canned

which will install it locally in node_modules, if you want to have it available from anywhere just install globally

$ npm install -g canned

How do I use it

There are 2 ways here, either you embed it somewhere programmatically

var canned = require('canned')
,   http = require('http')
,   opts = { logger: process.stdout }

can = canned('/path/to/canned/response/folder', opts)


Or just run the provided canned server script

$ canned

Which serves the current folder with canned responses on port 3000

$ canned -p 5000 ./my/responses/

will serve the relative folder via port 5000

If you need canned to respond with some delay, pass delay in ms to response_delay arg

$ canned --response_delay=1000 ./my/reponses/

If you want canned to iterate through all accepted content types in the Accept header, use

$ canned --relaxed_accept=true ./my/reponses/

If for whatever reason you want to turn of CORS support do so via

$ canned --cors=false ./my/responses/

Also if you need additional headers to be served alongside the CORS headers these can be added like this (thanks to runemadsen)

$ canned --headers "Authorization, Another-Header"

To enable CORS programmatically, you can use the following options:

var canned = require('canned')
,   http = require('http')
,   opts = {
        cors: true,
        cors_headers: ["Content-Type", "Location"]

Optionally, the cors_headers value can be a comma-separated string, as per the CLI option.

Other optional options include:

var opts = {
        sanitize: false, // get responses as is without any sanitization
        response_delay: 2000, // delay the response for 2 seconds
        relaxed_accept: true // iterate through all accepted content types in the `Accept` header
        wildcard: 'myany', // specify 'wildcard' directory, e.g. ./canned/api/users/myany/index.get.json

For more information checkout the pull request

Already using grunt? Great there is a plugin for that, thanks to jkjustjoshing.

It does not work :(

canned not found

make sure you either install globally or put ./node_modules/.bin in your PATH

it is still not found, and I installed globally

make sure /usr/local/share/npm/bin is in your path, this should be true for every install since you won’t be able to run any global module bins if not. (like express, and such)

the encoding looks wrong

make sure you run a version of node which is 0.10.3 or higher, because it fixes a problem for the encoding handling when reading files

My JSON request body is not matching any responses

Set the “Content-Type” header to contain “application/json”.

How to Contribute

I try to review the pull requests as quickly as possible, should it take to long feel free to bug me on twitter

Release History














everything before



MIT 2013 Philipp Fehre alias @sideshowcoder, or @ischi on twitter