projection integration test based on event- and query-messages

showcase-quarkus-eventsourcing/src/test/java/io/github/joht/showcase/quarkuseventsourcing/query/model/account/AccountProjectionTest.java

@@ -0,0 +1,59 @@
+package io.github.joht.showcase.quarkuseventsourcing.query.model.account;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.UUID;
+import java.util.concurrent.ExecutionException;
+
+import javax.inject.Inject;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import io.github.joht.showcase.quarkuseventsourcing.message.common.Nickname;
+import io.github.joht.showcase.quarkuseventsourcing.message.event.account.AccountCreatedEvent;
+import io.github.joht.showcase.quarkuseventsourcing.message.event.account.NicknameChangedEvent;
+import io.github.joht.showcase.quarkuseventsourcing.message.event.account.NicknamePresetEvent;
+import io.github.joht.showcase.quarkuseventsourcing.message.query.account.AccountNicknameQuery;
+import io.github.joht.showcase.quarkuseventsourcing.messaging.query.boundary.EventPublishingService;
+import io.github.joht.showcase.quarkuseventsourcing.messaging.query.boundary.QuerySubmitterService;
+import io.quarkus.test.junit.QuarkusTest;
+
+/**
+ * Read-Side (Integration-)Test that operates on message level. 
+ * <p>
+ * This is a black-box test. Published events represent the input. Query messages return the output,
+ * that is compared to the expected values. 
+ * Given that there is no pre-existing state, the test is perfectly reconstructible and repeatable.
+ * <p>
+ * This test also shows the strength of a CQRS-Read-Side (Projection) that ideally only depends 
+ * on the events it consumes and its current state. 
+ * Test cases can be completely described as a sequence of events.
+ */
+@QuarkusTest
+class AccountProjectionTest {
+
+	@Inject
+	EventPublishingService eventGateway;
+
+	@Inject
+	QuerySubmitterService queryGateway;
+
+	@Test
+	@DisplayName("After a account had been created and the nickname had been changed the new nickname is returned by the query")
+	void nicknameChangeQueryable() throws InterruptedException, ExecutionException {
+		String accountId = createTestAccountId();
+		Nickname expectedNickname = Nickname.of("Eddie");
+
+		eventGateway.publish(new AccountCreatedEvent(accountId));
+		eventGateway.publish(new NicknamePresetEvent(accountId, Nickname.none()));
+		eventGateway.publish(new NicknameChangedEvent(accountId, expectedNickname, Nickname.none()));
+
+		Nickname nickname = queryGateway.query(new AccountNicknameQuery(accountId), Nickname.class).get();
+		assertEquals(expectedNickname, nickname);
+	}
+
+	private String createTestAccountId() {
+		return getClass().getSimpleName() + "-accountId-" + UUID.randomUUID();
+	}
+}