Robot Framework, REST and JSON with RESTinstance

This is mostly a follow-up of the article Robot Framework, REST and JSON. As this article is now 5 years old, situation has evolved a bit, and recently a new REST library for Robot Framework got some attention: RESTinstance. So let’s take a quick look at it.

Before testing this new lib, let’s rewind a bit. First we need a product to test via a REST API and we will choose one that returns a JSON. For example a GET on should return:

   "api": "rest",
   "framework": "robot-framework"

Here is how we checked the response of that endpoint in the previous article using requests library:

*** settings ***
Library  Collections
Library  requests
*** test cases ***
    ${result} =  get
    Should Be Equal  ${result.status_code}  ${200}
    ${json} =  Set Variable  ${result.json()}
    ${framework} =  Get From Dictionary  ${json}  framework
    Should Be Equal  ${framework}  robot-framework
    ${api} =  Get From Dictionary  ${json}  api
    Should Be Equal  ${api}  rest

And here is how it can be checked using RESTinstance library:

*** settings ***
Library  REST
*** test cases ***
    GET  /framework/robot-framework/api/rest
    Object  response body
    String  response body api  rest  
    String  response body framework  robot-framework

So when we do a GET, we create a new instance of an object that can then be used by the other keywords of the library. This object can be written on the console log using Output keyword. In my case I get this output:

The current instance as JSON is:
    "spec": {},
    "request": {
        "body": null,
        "scheme": "http",
        "sslVerify": true,
        "headers": {
            "Content-Type": "application/json",
            "Accept": "application/json, */*",
            "User-Agent": "RESTinstance/1.0.0b35"
        "allowRedirects": true,
        "timestamp": {
            "utc": "2018-08-15T19:23:04.046254+00:00",
            "local": "2018-08-15T21:23:04.046254+02:00"
        "netloc": "",
        "url": "",
        "cert": null,
        "timeout": [
        "path": "/framework/robot-framework/api/rest",
        "query": {},
        "proxies": {},
        "method": "GET"
    "response": {
        "seconds": 0.173237,
        "status": 200,
        "body": {
            "framework": "robot-framework",
            "api": "rest"
        "headers": {
            "Content-Length": "56",
            "Server": "Google Frontend",
            "X-Cloud-Trace-Context": "8e86c2afa42b5380847247dbdc8a7e24",
            "Date": "Wed, 15 Aug 2018 19:23:03 GMT",
            "Access-Control-Allow-Origin": "*",
            "Content-Type": "application/json; charset=ISO-8859-1"
    "schema": {
        "exampled": true,
        "version": "draft04",
        "request": {
            "body": {
                "type": "null"
            "query": {
                "type": "object"
        "response": {
            "body": {
                "required": [
                "type": "object",
                "properties": {
                    "framework": {
                        "enum": [
                        "type": "string",
                        "example": "robot-framework"
                    "api": {
                        "enum": [
                        "type": "string",
                        "example": "rest"

So when we do String   response body api   rest we are exploring this object and checking the content of [“response”][“body”][“api”] but as we can see there is much more that can be checked. This syntax was a bit unexpected for me but I guess one just has to get used to it.

The library is also quite powerful in terms of JSON schema checking (and generation). I invite you to check the README to explore it further.

11 thoughts on “Robot Framework, REST and JSON with RESTinstance

  1. Hello Laurent, I m trying a POST method, running into error due to the quotes on the body – Serialized Order Query: “{ completedOrders : { numberOfDays: 30 } }”
    – error attempting ready order query com.peapod.util.RequestReader$RequestReadException: Unable to read instance of class class

    Any suggestion to send the body without the quotes?

    • Hi,
      please share more details about what/how you are trying to do. Show some Robot Framework code that you are using so that we can help.

      • Hi,
        i am tying to run below
        POST Statement On User API
        set headers for session
        POST /api/v4.0/user/${userId}/orders/query { completedOrders : { numberOfDays: 30 } }
        output response body
        Integer response status 200

        In server log i see the call as below when i run robot. I get a 400 bad request.
        Serialized Order Query: “{ completedOrders : { numberOfDays: 30 } }”

        Now the when i hit the api from browser in server logs i see as below without quotes on the body, which returns valid response.
        Serialized Order Query: { completedOrders : { numberOfDays: 30 } }

  2. Hi,
    How could I get a value of response as string and compare it to a partial string.
    I have found that
    ${resp_string}= String response body api
    Should Contain ${resp_string} re

    does not work. says ‘[“rest”]’ does not contain ‘re’

  3. hi,
    im desesperate …you can help me
    i was tried to post with the data below and the output is not correct json output i guess, how can make output without the character ‘u’
    {u’username’: u’my name’, u’password’: u’my password’, u’grant_type’: u’password’, u’client_id’: u’Pular’}

  4. Hi Laurent,

    I’m trying to run get from REST API.
    Here is the snippets of my code.
    But its throws an error.
    ValueError: Could not parse ‘

    Error 404 Not Found

    HTTP ERROR 404
    Problem accessing / Reason:
    Not Found

    ‘ as JSON: No JSON object could be decoded


    *** Settings ***
    Library OperatingSystem
    Library Collections
    Library json
    Library String
    Library HttpLibrary.HTTP
    Library RequestsLibrary
    Library JSONLibrary
    Library DataDriver test.xlsx sheet_name=Sheet1

    Suite Setup create the session
    Test Template check_api
    Suite Teardown close session
    *** Variables ***
    ${result} Mount point does not exist.
    ${timeout} 1s
    ${invalid} Invalid Parameter
    *** Test Cases ***
    *** Keywords ***
    create the session
    ${user_pass}= create list admin admin
    create session mysession ${base_url} auth=${user_pass}
    [Arguments] ${url}
    ${headers}= create dictionary Content-Type=application/json
    ${res}= get request mysession ${url} headers=${headers}
    sleep ${timeout}
    ${res1}= set variable ${res.status_code}
    ${res2}= set variable ${res.content}
    ${res3}= get json value ${res2} /errors/error/0/error-message
    Run Keyword If ‘${res1}’ == ‘200’ check_200 ${res2}
    … ELSE IF ‘${res1}’ == ‘404’ check_404 ${res2}
    … ELSE IF ‘${res1}’ == ‘500’ check_500 ${res2}
    … ELSE check_404! ${res1} ${res2}
    [Arguments] ${res2}
    log 200
    log many ${res2}

    [Arguments] ${res2}
    ${res3}= get json value ${res2} /errors/error/0/error-message
    log 404
    log json ${res2}
    should not be equal ${res3} ${result}
    [Arguments] ${res2}
    ${res3}= get json value ${res2} /errors/error/0/error-info
    ${res4}= Get Regexp Matches ${res3} message=(\\w+ \\w+) 1
    ${res5}= set variable ${res4[0]}
    log 500
    log json ${res2}
    should be equal ${res5} ${invalid}
    [Arguments] ${res1} ${res2}
    log ${res1}
    log json ${res2}
    should be equal ${res1} 200
    close session
    delete all sessions

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