Basically the problem is that when one of our datasource methods triggers an error then theerrorFromResponse method is called and then the error is returned and we see that error in our playground but when you try to test it and mock the error in your test the error you get from query/mutation method fromapollo-server-testing are both different.

In this PR to reproduce this issue what I've done is I changed the endpoint of spaceX and made it point tolaunch instead oflaunches which doesn't exist so the datasource method will get triggered and then I've overwrittenerrorFromResponse to handle the errors and what I'm doing there is I'm sending aApolloError with custom message.

Now when you open it in playground and run the querygetLaunchById it'll throw the error and the error object looks something like this

{"errors": [    {"message":"NOT_FOUND","locations": [        {"line":13,"column":3        }      ],"path": ["launch"],"extensions": {"code":"Not Found","response": {"url":"https://api.spacexdata.com/v2/launch?flight_number=123","status":404,"statusText":"Not Found","body":"Not Found"        },"exception": {"stacktrace": ["Error: NOT_FOUND","    at LaunchAPI.errorFromResponse (/Users/kamlesh/razorpay/fullstack-tutorial/final/server/src/datasources/launch.js:53:15)","    at processTicksAndRejections (internal/process/task_queues.js:93:5)"          ]        }      }    }  ],"data": {"launch":null  }}

Now I want to test this and assert that my error object is same as one returned when I actually run this query. So what I did was in my test I just mock the datasourceget method and reject it's value withNot Foundhere at this line but now when I execute my query inside the test the response object returned(which is error object) inside my test is this

{"http": {"headers": {}  },"errors": [    {"message":"Unexpected error value:\"Not Found\"","locations": [        {"line":2,"column":3        }      ],"path": ["launch"],"extensions": {"code":"INTERNAL_SERVER_ERROR"      }    }  ],"data": {"launch":null  }}

and when I do
expect(res).toEqual(errorFromPlayground); it fails because obviously the two objects are different. Now the question is why are these objects different and how do I make this assertion pass?

Reproduces#154