I'm trying to understand how to write an assertion in postman that will verify there are no additional key:value pairs in an object. 

For example, here is some test data:

```
"testArray": [
{ 
  "key-1" : "value1a"
  "key-2" : "value2a"
},    
{ 
  "key-1" : "value1b"
  "key-2" : "value2b"
},
]

```

I can easily write an assertion to very that testArray has a length of '2', i can verify the actual values of the key value pairs are returning as expected. I'm having a problem figuring out how to figure out that a key-3 was NOT returned. 

Now, if I know what a possible key is, i can verify it comes in as 'undefined', but if I don't know the name of a potential key value pair I want to make sure that i can assert these are ONLY the options I want.

If there isn't a simple solution such as being able to count the number of key:value pairs in an object, would I need to go down the route of creating a loop to iterate through the objects in the array to compare them to a valid values list?