Code 418 is returned instead of 200 if not using "And header Accept = 'application/json'"

Hi 😃 I am new to API testing and I was testing out Karate to practice API testing but there was a weird thing that happened and I don’t know if it is an issue or a misunderstanding from my side.

I am trying testing against “https://restful-booker.herokuapp.com/” APIs … It is An API playground created by Mark Winteringham for those wanting to learn more about API testing and tools

I added my feature as follows:

  Scenario: POST /booking should return 200 status code
    Given url 'https://restful-booker.herokuapp.com/booking'
    And request read('post_booking_data.json')
    When method POST
    Then status 200

It didn’t work and returned “418” although when I try the exact thing with postman, the 200 status code is returned successfully. But then after reading another part in Karate documentation, I updated my feature to be as follows:

  Scenario: POST /booking should return 200 status code
    Given url 'https://restful-booker.herokuapp.com/booking'
    And request read('post_booking_data.json')
    And header Accept = 'application/json'
    When method POST
    Then status 200

This just went well and the test ran successfully only after I added “And header Accept = ‘application/json’”

Is there anything that I was doing wrong or I didn’t understand it correctly?

Thanks a lot!!

[AyaAkl25]

@ptrthomas I would like to thank you a lot for your answer. And I think, yes, the API I am trying on is badly designed as you said.

[ptrthomas]

@Aya-Akl I think Karate is working as designed. There are 2 things that are happening. First: while Karate will send the Content-Type header automatically depending on the type of the payload, Postman seems to go one step further and set the Accept header as well.

Second: the API here is (at least in my opinion) badly designed. Ideally, the API should assume the intended Accept to be same as the Content-Type if not specified by the user. Here is an example of another API (not created by Mark Winteringham 😉 that works as you would expect:

Scenario: POST /booking should return 201 status code
Given url 'https://jsonplaceholder.typicode.com/users'
And request
"""
{
  "name": "Test User",
  "username": "testuser",
  "email": "[e-mail]",
  "address": {
    "street": "Has No Name",
    "suite": "Apt. 123",
    "city": "Electri",
    "zipcode": "54321-6789"
  }
}
"""
When method post
Then status 201

You can also try setting the Accept to application/xml in your example and see what happens.