How to set up backend API mocks in JavaScript.

Why mock an API?

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There are many benefits of API Mocks:

1. Developing frontend components that normally depend upon the services, when the services are not available;
2. Testing frontend components (frontend unit tests generally use mocks for more reliability); and
3. If backend and frontend development are happening in parallel, providing a contract/dummy response to work with whilst the backend is in development. ​ ## How to mock ​ In the following example, I will be using mountebank. There are other solutions out there, but we'll be using this one for the purposes of this article. ​
4. Install mountebank globally: npm install -g mountebank
5. Install the mountebank helper in your project: npm install mountebank-helper

6. Create a file nameed mbSetting.js and write:
   ​
   

   const mbHelper = require("mountebank-helper");
   // create a imposter, and assign a port number to it
   const imposter = new mbHelper.Imposter({ imposterPort: 3430 });
   // define an object as HTTP response
   const mockResponse = {
     uri: "/structure",
     verb: "GET",
     res: {
       statusCode: 200,
       responseHeaders: { "Content-Type": "application/json" },
       responseBody: JSON.stringify({
         Contents: [{ Key: "content1" }, { Key: "content2" }]
       })
     }
   };
   // bind the response object to a route
   imposter.addRoute(mockResponse);
   // start mb server with routes set before
   mbHelper.startMbServer(2525).then(function() {
     imposter.postToMountebank().then(() => {
       console.log("Imposter Posted, domain is http://localhost:3430");
     });
   });
   

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1. Start the mountebank server: mb --nologfile
2. Run the Node.js file you just created: node mbSetting.js

3. Send an HTTP request to http://localhost:3430/structure, and the response from this endpoint should be:
   ​
   

    [{ Key: "content1" }, { Key: "content2" }]
   

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