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Postman Local Mock Server

npm version

This project brings Postman's collection mocking capability locally enabling you to create mock servers quickly and run tests against these.

Quick Start

npm install -g @jordanwalsh23/postman-local-mock-server
postman-local -c path/to/collection.json -p 8080

Capabilities

  • Create a local mock server by supplying a Postman Collection.
  • Customizable TCP Port number for your mock server.
  • Supports the x-mock-response-name and x-mock-response-code headers to specify the response you want returned by either name or status code.
  • Supports the x-mock-match-request-headers header to match only the responses that contain a specific header.
  • Supports the x-mock-match-request-body header to match responses on POST/PATCH/PUT requests.
  • Full support for Postman's dynamic variables in example responses.
  • Support for wildcard variables in response examples.
  • Support for TLS enabled servers by supplying key/certificate.
  • Supports a local cache for performance testing.

CLI Options

--collection, -c : Path to your collection file
--port, -p       : Port you would like to use to host the server 0-65535
--key            : Path to Private Key file for TLS protected servers
--cert           : Path to Certificate file for TLS protected servers
--debug, -d      : Print debug statements to console when running.
--cacheTTL       : The time to keep responses in cache - see apicache for options.

Using in your project

  1. Run npm install @jordanwalsh23/postman-local-mock-server
  2. Add the dependency to your project and start the server.
const PostmanLocalMockServer = require('@jordanwalsh23/postman-local-mock-server');

let options = {
  port = 3555
}

//Create the collection object.
options.collection = JSON.parse(fs.readFileSync('./test/test-collection.json', 'utf8'));

//Create a new server
let server = new PostmanLocalMockServer(options);

//Start the server
server.start();

//Run some requests against your server
axios.get(`http://localhost:3555`).then(res => {
  //do something with the mocked response.
});

//Stop the server
server.stop();
  1. The server will now have endpoints available that match your specified collection.

Caching

This project includes a local cache that can be enabled via the CLI with the --cacheTTL flag or as an object when starting your server e.g.

//Start the server
server.start({
    cache: true,
    cacheOptions: {
        defaultDuration: "500ms"
    }
})

The defaultDuration and cacheTTL parameters must either specify a number of milliseconds, or use plain text english. Some valid examples:

defaultDuration: "500ms" 
defaultDuration: "1 minute" 
defaultDuration: "5 minutes" 
defaultDuration: "1 hour" 
defaultDuration: "1 day"

Clearing the cache

Restarting the server will automatically clear the in-memory cache, however if you want to clear the cache while the server is still running you can use the following endpoint:

DELETE http://localhost:<PORT>/cache

204 No Content

Unfortunately this will clash if there is an endpoint in your supplied collection with the path /cache. In that instance you can fork a copy of the source code and change this path manually.

Known Issues/Limitations

Tests/Prerequest scripts are not executed

This emulates the endpoints of a collection and the associated example responses. It does not invoke the pre-request or test scripts within a request.

As such, any requests that are reliant on variables (either collection/environment or global) will not work in this library.

Responses for the same path will take the first available

If your collection has the same path (e.g. /api/products) available multiple times, the first response defined will be the one returned by default - regardless of whether this is a successful or error response code.

There are several ways to overcome this:

  • Use the x-mock-response-name header on your requests to name the mock response you want returned.
  • Use the x-mock-response-code header on your requests to specify the response code (e.g. 200, 404) you want returned.

If you still cannot get the server to return your specific response, create an issue on this repo with the collection supplied and we'll try to replicate.

Request Matching algorithm differs from official Postman algorithm

  • This library uses a scoring based algorithm that mirrors closely, but does not fully match the official algorithm
  • Differences include:
    • If x-mock-response-code is used and multiple items are found the algorithm will just return the first item instead of prioritising the 2xx response.
    • If the document distance algorithm is used as no other matches can be found, the first result that meets the criteria is returned instead of calculating all responses and returning the highest score.

Contributions

Contributions are welcome on this repo. Submit issues or PRs and these will be reviewed for merging.

License

See the LICENSE file.