How to check if a message with a certain 'key' arrives exactly once while simulating a consumer for Kafka (JSON via AVRO) in ReadyAPI

I need to subscirbe to a topic in Kafka and check, that a specific message, with specific 'key' arives exactly once to the topic.

A JSONPath Match Assertion with JSONPath expression $['key'] and with appropiate Expected Result 'myKeyValue' ist true for the expected message and false for the other messages.

However, I don't see any possibility to count how often a message with $['key'] equals 'myKeyValue' arives and more over, to check, that this happens exactly once.

May be this is possible using script assertion only. However, I do not see how. If you have an script assertion example for counting arrived messages with $['key'] value equals 'myKeyValue' this would be great.

Any suggestions?

What is the final aimt?

I run end 2 end tests from TestComplete. At some step, the actions on the client must trigger a Kafka message. Via TestComplete ReadyAPI_step, I want to check, that the expected message is send, and this one is send only once. That's the aim.

What I did so far - Part I - no code:

I am using an AND-group of JSONPath Match assertions inside an OR-group.

One JSONPath Match Assertion in the AND-group 'selects' the message of interest by checking the value of $['key'] element of the JSON message.

The other JSONPath Match assertions in the AND-group checks the other members of the JSON Message for correctness.

In the OR-group is at the same level of the AND-group a sigle Smart Assertion.

The Smart Assertion is true for all messages but the one I am looking for. (I.e.: $['key'] is not 'myKeyValue')

This seems to be close to what we need. However:

I have the problem, that all of this is also true if the one message we are looking for does not arrives and even if no message arrives at all.

What I did so far - Part II - trying to code:

I try to write a Script assertion to count how often we get the expected Message.

One problem here: The code runs each time a message arrives.

To solve this, the counter should be saved in a text file in the file system.

The file contains one line; the line contains one single integer; the line is overwritten (i++) each time the assertion runs.

The idea should work.

Now, the shamefull points and questions about this. - The code does not work as expected:

1. No file is created
2. I am not able to write code that prints some simple info message to ReadyAPI log, either to the ReadyAPI GUI, nor to one of the famous logfiles present in %userprofile%.soapui or %userprofile%.readyapi\logs
3. How can I access to ReadyAPI project properties in the groovy script? I need this, for example, to set the file name from TestComplete as ReadyAPI project variable. Hint: this is NOT the answer: com.eviware.soapui.model.testsuite.TestRunContext.hasProperty("myProjectPropertyName")
4. How can I access to the Kafka message contents, in particular the value of $['key']?

About Question 4: The ReadyAPI documentation for script assertion refers to messageExchange interface. However, I have the feeling, that this class is suited for XML content only instead of JSON. Using messageExanche.getRawRequestData() may be an alternative. However - general speaking: It is not clear, which classes are available in ReadyAPI scripting assertion at all or which classes are available to convert a JSON string to an object or to parse the JSON directly. (Package jackson, for example, is not available, no matter import jackson.*).

An example for solving questions 1 to 4 or some of them would be great!

Thank you very much for your precious time!

With the valuable help of the SmartBear support team, I can write a Script Assertion (belonging to the subscriber step) to count messages that are received as subscriber and meet a certain criteria. Here is the example:

def messages = context.getCurrentStep().data
//
// Sample messages subscriber receive:
// {    "favorite_city" : "Berlin", "favorite_number" : 2, "favorite_color" : "white" }
// {    "favorite_city" : "Hamburg", "favorite_number" : 8, "favorite_color" : "purple" }
// {    "favorite_city" : "Cologne", "favorite_number" : 2, "favorite_color" : "black" }
//
// We are looking for messages containing favorite_number == 8, the 'valid' messages. 
def validMessage = "\"favorite_number\" : 8"; 
//
def validCounter = 0; // for counting valid messages.
//
// The project variable named global.numberof.expectedmessages contains the number of valid messages we expect.
// Of course, you may write here the number of valid messages you expect directly.
// However, this give you an answer for question 3 in the original post: access to project variables, which is the natural way to access them in ReadyAPI.
def globalNrOfExpectedMsgs = Integer.valueOf (context.expand( '${#Project#global.numberof.expectedmessages}' ) );
//
log.info "Validate count for following message:" + validMessage;
log.info "Expected Number of valid messages: " + globalNrOfExpectedMsgs;
//
// Check the messages 
for(message in messages){
    // variable message is the message data itself as string. 
    // This is the answer to question 4 in original post
    if (message.replace("\\n","").replace("\\","").contains(validMessage)){
        // A valid message found! Count it!
        validCounter++;
    }
}
//
log.info "Number of received valid messages: " +  validCounter
//
assert (validCounter == globalNrOfExpectedMsgs);

To check further attributes in the received messages, the script assertion can certainly be extended.

Because I would like to avoid coding for this, the final solution in our case will be a combination of the assertion contained here to ensure that the expected message arrives as often as expected and my first attempt called “no code”, as explained in the original post.

By the way: This post does not contain answers to questions 1 and 2 of the original posting. We can live without them for the moment.

I hope this helps you any way.