How to resolve Value cannot be null.\r\nParameter name: testResults while adding a test result using Visual Studio Rest API

I'm trying to upload the test case result into MTM using Visual Studio Rest API.

Followed the steps given in https://www.visualstudio.com/integrate/api/test/results#Addtestresultstoatestrun

But POST call throws Status: 400 Bad Request.

Response: 

{
    "$id": "1",
    "innerException": null,
    "message": "Value cannot be null.\r\nParameter name: testResults",
    "typeName": "System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089",
    "typeKey": "ArgumentNullException",
    "errorCode": 0,
    "eventId": 0
}

Can somebody help how to resolve this issue?