Axon State-Stored Aggregate Test IllegalStateException - spring-boot

Question

PROBLEM: Customer technical limitations force me to use Axon with state-stored Aggregates in PostgreSQL. I try a simple JPA-Entity Axon-Test and get IllegalStateException.
RESEARCH: A simplified project on the case is available at https://gitlab.com/ZonZonZon/simple-axon.git
In my test on
fixture.givenState(MyAggregate::new)
.when(command)
.expectState(state -> {
System.out.println();
});
I get
The state of this aggregate cannot be retrieved because it has been modified in a Unit of Work that was rolled back
java.lang.IllegalStateException: The state of this aggregate cannot be retrieved because it has been modified in a Unit of Work that was rolled back
at org.axonframework.common.Assert.state(Assert.java:44)
QUESTION: How to test an aggregate state using Axon and escape the error?

Answer 1

there are some missing parts in your project to let the test run properly. I will try to tackle them as concisely as possible:
your Command should contain the piece of information that connects it to the Aggregate. #TargetAggregateIdentifier is the annotation provided by the framework that connects a certain field to its #AggregateIdentifier counterpart into your Aggregate. You can read more here https://docs.axoniq.io/reference-guide/implementing-domain-logic/command-handling/aggregate#handling-commands-in-an-aggregate.
Said so, a UUID field needs to be added to your Create command.
This information will be then passed into the Created event : events are stored and can be processed both by a replay or an Aggregate re-hydration (upon client’s restart). (These) are the source of truth for our information.
#EventSourcingHandler annotated method will be responsible for applying the event and updating the #Aggregate values
public void on(Created event) {
uuid = event.getUuid();
login = event.getLogin();
password = event.getPassword();
token = event.getToken();
}
the test will then look like
public void a_VideochatAccount_Created_ToHaveData() {
Create command = Create.builder()
.uuid(UUID.randomUUID())
.login("123")
.password("333")
.token("d00a1f49-9e37-4976-83ae-114726938c73")
.build();
Created expectedEvent = Created.builder()
.uuid(command.getUuid())
.login(command.getLogin())
.password(command.getPassword())
.token(command.getToken())
.build();
fixture.givenNoPriorActivity()
.when(command)
.expectEvents(expectedEvent);
}
This test will validate your Command Part of your CQRS.
I will then suggest to separate the Query Part from your #Aggregate: you will then need to handle events with #EventHandler annotation placed on a method into a Projection #Component class, and implement the piece of logic that will take care of storing the information in the form that you need into PostgreSQL #Entity, using the #Repository JPA way, which I am sure you are familiar with.
You can find useful information on the ref guide https://docs.axoniq.io/reference-guide/implementing-domain-logic/event-handling following the video example on The Query Model based on code that you can be found in this repo https://github.com/AxonIQ/food-ordering-demo/tree/master
Hope that all is clear,
Corrado.