API by Example (ABE) is a format that can be used as a contract between services, describe APIs in a format that can be programmatically consumed by tools.
The main idea behind it is to illustrate how an API works via concrete examples, that can be used to generate tests, stubs and documentation for a given API.
API by Example was born out of the work its initial authors have been doing at Rockabox, while developing better ways to test API producers and consumers.
The format is initially limited to HTTP-based APIs, and optimised for (but not limited to) APIs that exchange JSON data.
The main building block of ABE is a JSON file that illustrates one API call. One API call is an HTTP request that consists of a URL (pattern), sample request data and sample response data. Additional fields are included for documentation purposes.
A schema describing the ABE format using JSON Schema can be found in schema.json
The skeleton of an ABE file is:
{
"description": "<description>",
"url": "<url>",
"method": "<http method>",
"examples": {
"<label>": {
"description": "<description>",
"request": {
"queryParams": <params>,
"headers": <headers>,
"body": <body>
},
"response": {
"status": <status>,
"headers": <headers>,
"body": <body>
}
}
}
}descriptionis an optional text describing the API or the concrete exampleurlis a base location for our API.examplescontains your different API examples for the contract, this can be in the form of anarrayor anobject.labelis an arbitrary label that you can use to refer to one concrete example, useful when you want to include more than one possible responses. For instance,"OK"and"Not found", or"Empty"versus"One"versus"Many".http methodis one of the HTTP verbsGET,POST,PUT...paramsare query string parameters to add to the URLheadersis an optional object mapping headers to valuesstatusis HTTP status:200,404, etc...bodyis the payload, in JSON format, or a properly escaped string. Binary encodings are not supported at the moment.
To illustrate with a concrete example:
{
"description": "Retrieve a list of brands",
"url": "/campaigns/brands/",
"method": "GET",
"examples": {
"OK": {
"description": "Collection found",
"request": {
"url": "/campaigns/brands/",
"queryParams": {},
"body": {}
},
"response": {
"status": 200,
"body": [
{
"id": 1,
"name": "Microsoft"
},
{
"id": 2,
"name": "Monsoon"
},
{
"id": 3,
"name": "Mars"
},
{
"id": 4,
"name": "John Lewis"
}
]
}
}
}
}