How to fail a Gatling test from within "exec"?

Question

A Gatling scenario with an exec chain. After a request, returned data is saved. Later it's processed and depending on the processing result, it should either fail or pass the test.

This seems like the simplest possible scenario, yet I can't find any reliable info how to fail a test from within an exec block. assert breaks the scenario and seemingly Gatling (as in: the exception throw doesn't just fail the test).

Example:

// The scenario consists of a single test with two exec creating the execChain
val scn = scenario("MyAwesomeScenario").exec(reportableTest(

     // Send the request
     exec(http("127.0.0.1/Request").get(requestUrl).check(status.is(200)).check(bodyString.saveAs("MyData")

     // Process the data
    .exec(session => { 
         assert(processData(session.attributes("MyData")) == true, "Invalid data");
    })
))

Above the scenario somewhere along the line "guardian failed, shutting down system".

Now this seems a useful, often-used thing to do - I'm possibly missing something simple. How to do it?

Answer 1

You have to abide by Gatling APIs.

1. With checks, you don't "fail" the test, but the request. If you're looking for failing the whole test, you should have a look at the Assertions API and the Jenkins plugin.
2. You can only perform a Check at the request site, not later. One of the very good reasons is that if you store the bodyString in the Sessions like you're doing, you'll end using a lot of memory and maybe crashing (still referenced, so not garbage collectable). You have to perform your processData in the check, typically in the transform optional step.