diff --git a/axon/src/main/java/com/baeldung/axon/commandmodel/MessagesAggregate.java b/axon/src/main/java/com/baeldung/axon/commandmodel/MessagesAggregate.java
deleted file mode 100644
index 1ab9501617..0000000000
--- a/axon/src/main/java/com/baeldung/axon/commandmodel/MessagesAggregate.java
+++ /dev/null
@@ -1,38 +0,0 @@
-package com.baeldung.axon.commandmodel;
-
-import static org.axonframework.modelling.command.AggregateLifecycle.apply;
-
-import org.axonframework.commandhandling.CommandHandler;
-import org.axonframework.eventsourcing.EventSourcingHandler;
-import org.axonframework.modelling.command.AggregateIdentifier;
-import org.axonframework.spring.stereotype.Aggregate;
-
-import com.baeldung.axon.coreapi.commands.CreateMessageCommand;
-import com.baeldung.axon.coreapi.commands.MarkReadMessageCommand;
-import com.baeldung.axon.coreapi.events.MessageCreatedEvent;
-import com.baeldung.axon.coreapi.events.MessageReadEvent;
-
-@Aggregate
-public class MessagesAggregate {
-
-    @AggregateIdentifier
-    private String id;
-
-    public MessagesAggregate() {
-    }
-
-    @CommandHandler
-    public MessagesAggregate(CreateMessageCommand command) {
-        apply(new MessageCreatedEvent(command.getId(), command.getText()));
-    }
-
-    @CommandHandler
-    public void handle(MarkReadMessageCommand command) {
-        apply(new MessageReadEvent(id));
-    }
-
-    @EventSourcingHandler
-    public void on(MessageCreatedEvent event) {
-        this.id = event.getId();
-    }
-}
\ No newline at end of file
diff --git a/axon/src/main/java/com/baeldung/axon/commandmodel/OrderAggregate.java b/axon/src/main/java/com/baeldung/axon/commandmodel/OrderAggregate.java
new file mode 100644
index 0000000000..fd4f901032
--- /dev/null
+++ b/axon/src/main/java/com/baeldung/axon/commandmodel/OrderAggregate.java
@@ -0,0 +1,58 @@
+package com.baeldung.axon.commandmodel;
+
+import static org.axonframework.modelling.command.AggregateLifecycle.apply;
+
+import org.axonframework.commandhandling.CommandHandler;
+import org.axonframework.eventsourcing.EventSourcingHandler;
+import org.axonframework.modelling.command.AggregateIdentifier;
+import org.axonframework.spring.stereotype.Aggregate;
+
+import com.baeldung.axon.coreapi.commands.ConfirmOrderCommand;
+import com.baeldung.axon.coreapi.commands.PlaceOrderCommand;
+import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
+import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
+import com.baeldung.axon.coreapi.events.OrderPlacedEvent;
+import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+
+@Aggregate
+public class OrderAggregate {
+
+    @AggregateIdentifier
+    private String orderId;
+    private boolean orderConfirmed;
+
+    @CommandHandler
+    public OrderAggregate(PlaceOrderCommand command) {
+        apply(new OrderPlacedEvent(command.getOrderId(), command.getProduct()));
+    }
+
+    @CommandHandler
+    public void handle(ConfirmOrderCommand command) {
+        apply(new OrderConfirmedEvent(orderId));
+    }
+
+    @CommandHandler
+    public void handle(ShipOrderCommand command) {
+        if (!orderConfirmed) {
+            throw new IllegalStateException("Cannot ship an order which has not ben confirmed yet.");
+        }
+
+        apply(new OrderShippedEvent(orderId));
+    }
+
+    @EventSourcingHandler
+    public void on(OrderPlacedEvent event) {
+        this.orderId = event.getOrderId();
+        orderConfirmed = false;
+    }
+
+    @EventSourcingHandler
+    public void on(OrderConfirmedEvent event) {
+        orderConfirmed = true;
+    }
+
+    protected OrderAggregate() {
+        // Required by Axon to build a default Aggregate prior to Event Sourcing
+    }
+
+}
\ No newline at end of file
diff --git a/axon/src/test/java/com/baeldung/axon/commandmodel/MessagesAggregateUnitTest.java b/axon/src/test/java/com/baeldung/axon/commandmodel/MessagesAggregateUnitTest.java
deleted file mode 100644
index 46357ddff8..0000000000
--- a/axon/src/test/java/com/baeldung/axon/commandmodel/MessagesAggregateUnitTest.java
+++ /dev/null
@@ -1,40 +0,0 @@
-package com.baeldung.axon.commandmodel;
-
-import java.util.UUID;
-
-import org.axonframework.test.aggregate.AggregateTestFixture;
-import org.axonframework.test.aggregate.FixtureConfiguration;
-import org.junit.*;
-
-import com.baeldung.axon.coreapi.commands.CreateMessageCommand;
-import com.baeldung.axon.coreapi.commands.MarkReadMessageCommand;
-import com.baeldung.axon.coreapi.events.MessageCreatedEvent;
-import com.baeldung.axon.coreapi.events.MessageReadEvent;
-
-public class MessagesAggregateUnitTest {
-
-    private FixtureConfiguration<MessagesAggregate> fixture;
-
-    @Before
-    public void setUp() {
-        fixture = new AggregateTestFixture<>(MessagesAggregate.class);
-    }
-
-    @Test
-    public void giveAggregateRoot_whenCreateMessageCommand_thenShouldProduceMessageCreatedEvent() {
-        String eventText = "Hello, how is your day?";
-        String id = UUID.randomUUID().toString();
-        fixture.given()
-                .when(new CreateMessageCommand(id, eventText))
-                .expectEvents(new MessageCreatedEvent(id, eventText));
-    }
-
-    @Test
-    public void givenMessageCreatedEvent_whenReadMessageCommand_thenShouldProduceMessageReadEvent() {
-        String id = UUID.randomUUID().toString();
-
-        fixture.given(new MessageCreatedEvent(id, "Hello :-)"))
-                .when(new MarkReadMessageCommand(id))
-                .expectEvents(new MessageReadEvent(id));
-    }
-}
\ No newline at end of file
diff --git a/axon/src/test/java/com/baeldung/axon/commandmodel/OrderAggregateUnitTest.java b/axon/src/test/java/com/baeldung/axon/commandmodel/OrderAggregateUnitTest.java
new file mode 100644
index 0000000000..e7dfdeb794
--- /dev/null
+++ b/axon/src/test/java/com/baeldung/axon/commandmodel/OrderAggregateUnitTest.java
@@ -0,0 +1,48 @@
+package com.baeldung.axon.commandmodel;
+
+import java.util.UUID;
+
+import org.axonframework.test.aggregate.AggregateTestFixture;
+import org.axonframework.test.aggregate.FixtureConfiguration;
+import org.junit.*;
+
+import com.baeldung.axon.coreapi.commands.PlaceOrderCommand;
+import com.baeldung.axon.coreapi.commands.ShipOrderCommand;
+import com.baeldung.axon.coreapi.events.OrderConfirmedEvent;
+import com.baeldung.axon.coreapi.events.OrderPlacedEvent;
+import com.baeldung.axon.coreapi.events.OrderShippedEvent;
+
+public class OrderAggregateUnitTest {
+
+    private static final String ORDER_ID = UUID.randomUUID().toString();
+    private static final String DEFAULT_PRODUCT = "Deluxe Chair";
+
+    private FixtureConfiguration<OrderAggregate> fixture;
+
+    @Before
+    public void setUp() {
+        fixture = new AggregateTestFixture<>(OrderAggregate.class);
+    }
+
+    @Test
+    public void giveNoPriorActivity_whenPlaceOrderCommand_thenShouldPublishOrderPlacedEvent() {
+        fixture.givenNoPriorActivity()
+               .when(new PlaceOrderCommand(ORDER_ID, DEFAULT_PRODUCT))
+               .expectEvents(new OrderPlacedEvent(ORDER_ID, DEFAULT_PRODUCT));
+    }
+
+    @Test
+    public void givenOrderPlacedEvent_whenShipOrderCommand_thenShouldThrowIllegalStateException() {
+        fixture.given(new OrderPlacedEvent(ORDER_ID, DEFAULT_PRODUCT))
+               .when(new ShipOrderCommand(ORDER_ID))
+               .expectException(IllegalStateException.class);
+    }
+
+    @Test
+    public void givenOrderPlacedEventAndOrderConfirmedEvent_whenShipOrderCommand_thenShouldPublishOrderShippedEvent() {
+        fixture.given(new OrderPlacedEvent(ORDER_ID, DEFAULT_PRODUCT), new OrderConfirmedEvent(ORDER_ID))
+               .when(new ShipOrderCommand(ORDER_ID))
+               .expectEvents(new OrderShippedEvent(ORDER_ID));
+    }
+
+}
\ No newline at end of file