I'm using k6 to test a token generator. I want to add a check to filter the success response with status code 200 and token must exist.

My current script is

  check(response, {
    "status equals 200": response => response.status.toString() === "200",
    "body contains access_token": response =>
      response.body.includes("access_token"),
  });

but it does not work and return an error

level=error msg="failed to handle the end-of-test summary" error="error handling summary object body contains access_token: invalid type map[string]interface {}, it needs to be a string, byte array or an ArrayBuffer"

Response example

Thank you guys for helping me !!