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1

I have a JSON response that looks like

{
“a”: “2025-08-28T16:53:16”,
“b”: 1756425196,
“a-b”: 323223
}

How to I refer to a-b in Post Processor Assertion.

for a I use $.a

2

To refer to the “a-b” field in Post Processor Assertion, you can use the JSONPath expression: $.['a-b'].

Hover over the right side of the response body field to see the assertion and variable extraction entry. Clicking the popup will auto-fill the JSONPath expression. If you don’t see the entry, please update to the latest version.

3

That worked. The only change made was to use double quotes because single quotes in Assertions caused an error.

4

It did not work. This works in a custom script. console.log(“expiration-date=” + pm.response.json()[“a-b”]);
but $.[‘a-b’] in Assertions shows this error. PostProcessor Script Error: Unexpected identifier ‘a’

5

You can use the assertion component for this, and I’ve confirmed it works. Please refer to the settings in the image.

b1f6e4b0-489a-412a-b364-f1930fefeb06.jpeg
b1f6e4b0-489a-412a-b364-f1930fefeb06.jpeg1511×510 72.4 KB

6

I confirm Equals works. My assertion uses Exists. Does it work for you?

7

I can confirm the issue with Exists is reproducible. We’re checking it now and will update you as soon as we have more information.

8

Thanks for the update. Is there a workaound. Can “Does Not Equal” be used and if so. How do I say != null as a way to achieve the same result as Exists. Let me know.

9

You can use a Custom Script to verify if this field exists. Here’s a script example for you:

const responseJson = pm.response.json();
// Assert that the $.['a-b'] field exists
pm.test("Check if 'a-b' field exists", function () {
    // Check if the field exists using hasOwnProperty method
    pm.expect(responseJson).to.have.property('a-b');

    // Alternatively, check if the field is not undefined
    // pm.expect(responseJson['a-b']).to.not.be.undefined;
});