AggregateTestFixture throws AggregateNotFoundException when a command handler with a creation policy applies no events

[mnegacz]

Basic information

• Axon Framework version: 4.5.10
• JDK version: OpenJDK Runtime Environment Temurin-11.0.14+9 (build 11.0.14+9)
• Complete executable reproducer if available (e.g. GitHub Repo): Test snippet included below

Steps to reproduce

Create a test case for an aggregate with a command handler that uses the creation policy @CreationPolicy(AggregateCreationPolicy.CREATE_IF_MISSING). The command handler shouldn't apply any events.

Reproducer:

import org.axonframework.commandhandling.CommandHandler;
import org.axonframework.modelling.command.AggregateCreationPolicy;
import org.axonframework.modelling.command.AggregateIdentifier;
import org.axonframework.modelling.command.CreationPolicy;
import org.axonframework.modelling.command.TargetAggregateIdentifier;
import org.axonframework.spring.stereotype.Aggregate;
import org.axonframework.test.aggregate.AggregateTestFixture;
import org.junit.jupiter.api.*;

public class SomeAggregateTest {

    private final AggregateTestFixture<SomeAggregate> testee = new AggregateTestFixture<>(SomeAggregate.class);

    @Test
    void publishesNoEventsOnSomeCommand() {
        testee.givenNoPriorActivity()
              .when(new SomeCommand("id"))
              .expectNoEvents();
    }

    @Aggregate
    public static class SomeAggregate {

        @AggregateIdentifier
        private String id;

        public SomeAggregate() {
        }

        @CreationPolicy(AggregateCreationPolicy.CREATE_IF_MISSING)
        @CommandHandler
        public void handle(SomeCommand command) {
            // no events applied
        }
    }

    public static class SomeCommand {

        @TargetAggregateIdentifier
        private final String id;

        public SomeCommand(String id) {
            this.id = id;
        }

        public String getId() {
            return id;
        }
    }
}

Expected behaviour

The test case passes. It works on Axon Framework version 4.5.9

Actual behaviour

The exception is thrown:

11:37:38.021 [main] DEBUG org.axonframework.modelling.command.LockingRepository - Exception occurred while trying to load an aggregate. Releasing lock.
org.axonframework.modelling.command.AggregateNotFoundException: No 'given' events were configured for this aggregate, nor have any events been stored.
	at org.axonframework.test.aggregate.AggregateTestFixture$RecordingEventStore.readEvents(AggregateTestFixture.java:873)
	at org.axonframework.eventsourcing@4.5.10/org.axonframework.eventsourcing.EventSourcingRepository.readEvents(EventSourcingRepository.java:147)
	at org.axonframework.eventsourcing@4.5.10/org.axonframework.eventsourcing.EventSourcingRepository.doLoadWithLock(EventSourcingRepository.java:124)
	at org.axonframework.eventsourcing@4.5.10/org.axonframework.eventsourcing.EventSourcingRepository.doLoadWithLock(EventSourcingRepository.java:52)
	at org.axonframework.modelling@4.5.10/org.axonframework.modelling.command.LockingRepository.doLoad(LockingRepository.java:128)
	at org.axonframework.modelling@4.5.10/org.axonframework.modelling.command.LockingRepository.doLoad(LockingRepository.java:56)
	at org.axonframework.modelling@4.5.10/org.axonframework.modelling.command.AbstractRepository.lambda$load$5(AbstractRepository.java:131)
	at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1134)
	at org.axonframework.modelling@4.5.10/org.axonframework.modelling.command.AbstractRepository.load(AbstractRepository.java:130)
	at org.axonframework.modelling@4.5.10/org.axonframework.modelling.command.AbstractRepository.load(AbstractRepository.java:177)
	at org.axonframework.test.aggregate.AggregateTestFixture.detectIllegalStateChanges(AggregateTestFixture.java:550)
	at org.axonframework.test.aggregate.AggregateTestFixture.when(AggregateTestFixture.java:454)
	at org.axonframework.test.aggregate.AggregateTestFixture.when(AggregateTestFixture.java:437)
	at com.example.test/com.example.test.SomeAggregateTest.publishesNoEventsOnSomeCommand(SomeAggregateTest.java:19) <31 internal lines>
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541) <9 internal lines>
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541) <25 internal lines>
11:37:38.022 [main] DEBUG org.axonframework.messaging.unitofwork.AbstractUnitOfWork - Rolling back Unit Of Work.
11:37:38.022 [main] DEBUG org.axonframework.messaging.unitofwork.MessageProcessingContext - Notifying handlers for phase ROLLBACK
11:37:38.022 [main] DEBUG org.axonframework.messaging.unitofwork.MessageProcessingContext - Notifying handlers for phase CLEANUP
11:37:38.022 [main] DEBUG org.axonframework.messaging.unitofwork.MessageProcessingContext - Notifying handlers for phase CLOSED

org.axonframework.test.AxonAssertionError: The working aggregate was not considered deleted, but the Repository cannot recover the state of the aggregate, as it is considered deleted there.

	at com.example.test/com.example.test.SomeAggregateTest.publishesNoEventsOnSomeCommand(SomeAggregateTest.java:19) <31 internal lines>
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541) <9 internal lines>
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1541) <25 internal lines>

[smcvb]

This turns out to be a bug that sneaked into the framework, but for Command Handlers that construct Aggregates in general.
Writing something like the following:

class MyAggregate {
    @CommandHandler
    public MyAggregate(MyCommand command) {
        if (someStateFromTheCommand) {
            apply(new SomeEvent());
        }
    }
}

Where the if-statement isn't met now results in an IllegalArgumentException that the "Aggregate identifier may not be null" from the PessimisticLockFactory.
Chances are this got introduced in pull request #1854.
As such, it's a part of Axon Framework since release 4.5.3.

As seen from the sample, this predicament does not limit itself to the Creation Policy logic.
The AggregateTestFixture just deals with the Creation Policy logic differently, causes the predicament to show up as off 4.5.10.

[smcvb]

I am closing this issue since pull request #2248 resolves it.