How to do simultaneous request calls using Postman collections

Newman is a command line collection runner for Postman. It allows you to run and test a Postman Collection directly from the command line. It is built with extensibility in mind so that you can easily integrate it with your continuous integration servers and build systems.

With Newman and Async, you can do simultaneous request calls which will be very helpful for performance tests.

Here are what you'll need to do to get it working:

1. Install Newman by following the instructions on http://blog.getpostman.com/2015/04/09/installing-newman-on-windows/
   In my case, I didn’t have to install Python to get it working.
2. Create/use a folder for the tests
3. Export a Postman collection into a file
   
4. Export a Postman environment that you want to invoke the calls to
   
5. Open a command prompt in administrator mode on the folder from step 2
6. Install async module by typing npm install --save async
7. Create a .js file

var path = require('path'),
  async = require('async'), //https://www.npmjs.com/package/async
  newman = require('newman'),

  parametersForTestRun = {
    collection: path.join(__dirname, 'postman_collection.json'), // your collection
    environment: path.join(__dirname, 'postman_environment.json'), //your env
  };

parallelCollectionRun = function(done) {
  newman.run(parametersForTestRun, done);
};

// Runs the Postman sample collection thrice, in parallel.
async.parallel([
    parallelCollectionRun,
    parallelCollectionRun,
    parallelCollectionRun
  ],
  function(err, results) {
    err && console.error(err);

    results.forEach(function(result) {
      var failures = result.run.failures;
      console.info(failures.length ? JSON.stringify(failures.failures, null, 2) :
        `${result.collection.name} ran successfully.`);
    });
  });



8. Run the .js file from step 7 from command prompt node fileName.js

More on Postman functions

Continuing from my posts on Postman, here are some of the Postman functions that I use from time to time.

1. To assign a value from the response to an environment variable:
   var json = JSON.parse(responseBody);
   postman.setEnvironmentVariable("bearerToken", json.access_token);
   
   In that example, it is assigning the access_token from the response to a variable called bearerToken
   
2. Test conditions to decide the test result. This is to make it easier to see which request is failing and which one is not failing.
   tests["Status OK"] = responseCode.code == 201
   
   In this case, Status OK will be considered to be failed if the response status code is NOT 201.
   
3. Randomise an integer between certain values
   _.random(1,5)
   
   In this case, it will return any integer number between 1 and 5.
   
4. Randomise an integer value
   {{$randomInt}}
   
   In this case, it will return a random integer number.
   
5. When you create a collection of requests in Postman, you can then run them using the collection runner. By default it will go by the request order in the collection. You can use this function to direct the sequence if you need to deviate from the default order:
   postman.setNextRequest("call name");
   If you put call that in the "Tests" script, then after running the current call, it will then run another call named "call name".
   
   postman.setNextRequest(null);
   The above will stop the execution.
   
   With this function you can basically call the same request more than once (for example to create multiple lines).
   Please note that this function only works in the Collection Runner.
   

In the next post, I will explain how to use Postman collection and environment data to do multiple concurrent calls, which will be very useful for performance tests.