Zeebe Test Engine throws IllegalStateException when ending a process with a Terminate End Event

[VonDerBeck]

Description

Given the following sample process:

In a process unit test using the embedded Zeebe Test Engine (zeebe-process-test-extension) I get the following error upon completing the User Task which is followed by the Terminate End Event:

2023-09-14T13:15:51.228+02:00 ERROR 15152 --- [    zb-actors-5] io.camunda.zeebe.broker.process          : Expected to process record 'TypedRecordImpl{metadata=RecordMetadata{recordType=COMMAND, valueType=JOB, intent=COMPLETE}, value={"deadline":-1,"worker":"","retries":-1,"retryBackoff":0,"recurringTime":-1,"type":"","customHeaders":[packed value (length=1)],"variables":"gA==","errorMessage":"","errorCode":"","bpmnProcessId":"","processDefinitionVersion":-1,"processDefinitionKey":-1,"processInstanceKey":-1,"elementId":"","elementInstanceKey":-1}}' without errors, but exception occurred with message 'Expected the child count to be positive but was -1'.

java.lang.IllegalStateException: Expected the child count to be positive but was -1
	at io.camunda.zeebe.engine.state.instance.ElementInstance.decrementChildCount(ElementInstance.java:111) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.state.instance.DbElementInstanceState.removeInstance(DbElementInstanceState.java:163) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.state.appliers.ProcessInstanceElementTerminatedApplier.applyState(ProcessInstanceElementTerminatedApplier.java:41) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.state.appliers.ProcessInstanceElementTerminatedApplier.applyState(ProcessInstanceElementTerminatedApplier.java:19) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.state.appliers.EventAppliers.applyState(EventAppliers.java:302) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.processing.streamprocessor.writers.ResultBuilderBackedEventApplyingStateWriter.appendFollowUpEvent(ResultBuilderBackedEventApplyingStateWriter.java:41) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.processing.bpmn.behavior.BpmnStateTransitionBehavior.transitionTo(BpmnStateTransitionBehavior.java:219) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.processing.bpmn.behavior.BpmnStateTransitionBehavior.transitionToTerminated(BpmnStateTransitionBehavior.java:209) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]
	at io.camunda.zeebe.engine.processing.bpmn.task.JobWorkerTaskProcessor.lambda$onTerminate$10(JobWorkerTaskProcessor.java:96) ~[zeebe-workflow-engine-8.2.13.jar:8.2.13]

I do not get these weird exceptions in case the end event is a simple End Event.

Expected behaviour

Completing a User Task followed by a Terminate End Event should not lead to a IllegalStateException when testing my process with the embedded test engine.

Reproduction steps

Run ProcessUnitTest in the following Maven project:

camunda-8-terminate-event.zip

Environment

• OS: Windows 10
• Zeebe 8.2.13, Java 17, Spring Boot 3.0.5

[namero999]

Most likely related #876

[korthout]

Thanks @VonDerBeck for raising this.

I'm closing this in favor of #876 as this is a duplicate. The reproducible example is useful. I'll make sure to track it in the other issue.