As part of my workshops, I offer support afterwards to help answer questions attendees have once they are back at work and applying what they’ve learnt in the real world. I was asked a question recently about Postman around sharing and comparing payloads across requests. It’s a question that has popped up a few times, so I thought I would share my solutions towards how you can get Postman to store payloads and then retrieve them to use as a comparator in later requests.

The problem

For this example, I will be using restful-booker which you can clone down and run yourself by following these instructions.

As part of my testing of restful-booker I have two endpoints that send me back the following responses:

POST /booking

{
  "bookingid": 12,
  "booking": {
    "firstname": "Sally",
    "lastname": "Brown",
    "totalprice": 111,
    "depositpaid": true,
    "bookingdates": {
      "checkin": "2013-02-23",
      "checkout": "2014-10-23"
    },
    "additionalneeds": "Breakfast"
  }
}

GET /booking/12

{
  "firstname": "Sally",
  "lastname": "Brown",
  "totalprice": 111,
  "depositpaid": true,
  "bookingdates": {
    "checkin": "2013-02-23",
    "checkout": "2014-10-23"
  },
  "additionalneeds": "Breakfast"
}

So I need to work out how I can compare the booking object that exists in the POST /booking response body to the booking object in the GET /booking/{id} and since restful-booker supports both XML and JSON how I can compare both formats.

Comparing XML Payloads

Firstly, click here to download the Postman collection to access the requests and tests. You will find that there are two requests, the first is creating a booking and the second is retrieving a booking. So let’s take a look at the code in the Test tab:

1. Create XML booking

var parsedResponse = xml2Json(responseBody);
postman.setGlobalVariable("created_id", parsedResponse['created-booking'].bookingid);

postman.setGlobalVariable("original_response", responseBody);

Let’s review this test code:

1. Responsebody is a special variable in Postman that stores the response body as a string meaning if we want to do something programmatic with the response body we need to parse it
2. xml2Json allows to easily convert an XML object into a object meaning we can call parsedResponse['created-booking'].bookingid to get the id we need for the next request
3. setGlobalVariable allows us to store values as strings this means if we want to store a payload we have to store it as a string. Attempting to store an object as a global variable will result in the string [object Object] being stored.

2. Get booking and assert

var currentResponse = xml2Json(responseBody);
var previousResponse = xml2Json(globals.original_response);

var flattenCurrentResponse = JSON.stringify(currentResponse.booking);
var flattenPreviousResponse = JSON.stringify(previousResponse['created-booking'].booking);

tests["Assert responses match"] = flattenCurrentResponse === flattenPreviousResponse;

Let’s review this test code:

1. We can get our stored environment variable by calling globals.orginal_response to get the response as a string
2. We have to use JSON.stringify to convert our objects back to strings as comparing objects in JavaScript is a tricky thing to do

Sharing JSON Payloads

Firstly, click here to download the Postman collection to access the requests and tests. You will find that there are two requests, the first is creating a booking and the second is retrieving a booking. So let’s take a look at the code in the Test tab:

1. Create XML booking

var parsedResponse = JSON.parse(responseBody);
postman.setGlobalVariable("created_id", parsedResponse.bookingid);

postman.setGlobalVariable("original_response", responseBody);

Let’s review this test code:

1. We use JSON.parse to parse the body as responseBody is stored as a string

2. Get booking and assert

var currentResponse = JSON.parse(responseBody);
var previousResponse = JSON.parse(globals.original_response);

var flattenCurrentResponse = JSON.stringify(currentResponse);
var flattenPreviousResponse = JSON.stringify(previousResponse.booking);

tests["Assert responses match"] = flattenCurrentResponse === flattenPreviousResponse;

Conclusion

So there you have two demonstrations of storing bodies across requests. The actual code required is quite simple but does require a few workarounds especially around the storing and retrieval of stored variables.

References

1. Environmental variables - https://www.getpostman.com/docs/environments
2. Reading environmental variables in the Test panel -http://stackoverflow.com/questions/21418529/how-do-i-read-environment-variables-in-postman-tests
3. Comparing Javascript Objects - http://stackoverflow.com/questions/1068834/object-comparison-in-javascript