Refactored the codebase.

java-es-cqrs/pom.xml

@@ -3,7 +3,7 @@
 	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.sapient.learning</groupId>
-	<artifactId>java-events</artifactId>
+	<artifactId>java-es-cqrs</artifactId>
 	<version>0.0.1-SNAPSHOT</version>
 	<name>java-es-cqrs</name>
 	<properties>
@@ -16,5 +16,12 @@
 			<artifactId>lombok</artifactId>
 			<version>1.18.12</version>
 		</dependency>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>4.13</version>
+			<scope>test</scope>
+		</dependency>
+
 	</dependencies>
 </project>

java-es-cqrs/src/main/java/com/baeldung/patterns/cqrs/projectors/UserProjector.java

@@ -3,6 +3,7 @@ package com.baeldung.patterns.cqrs.projectors;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 
 import com.baeldung.patterns.cqrs.repository.UserReadRepository;
@@ -21,36 +22,28 @@ public class UserProjector {
     }
 
     public void project(User user) {
-        UserContact userContact = readRepository.getUserContact(user.getUserid());
+        UserContact userContact = Optional.ofNullable(readRepository.getUserContact(user.getUserid()))
-        if (userContact == null)
+            .orElse(new UserContact());
-            userContact = new UserContact();
-        userContact.setContacts(user.getContacts());
         Map<String, Set<Contact>> contactByType = new HashMap<>();
         for (Contact contact : user.getContacts()) {
-            Set<Contact> contacts = contactByType.get(contact.getType());
+            Set<Contact> contacts = Optional.ofNullable(contactByType.get(contact.getType()))
-            if (contacts == null)
+                .orElse(new HashSet<>());
-                contacts = new HashSet<>();
             contacts.add(contact);
             contactByType.put(contact.getType(), contacts);
         }
         userContact.setContactByType(contactByType);
         readRepository.addUserContact(user.getUserid(), userContact);
 
-        UserAddress userAddress = readRepository.getUserAddress(user.getUserid());
+        UserAddress userAddress = Optional.ofNullable(readRepository.getUserAddress(user.getUserid()))
-        if (userAddress == null)
+            .orElse(new UserAddress());
-            userAddress = new UserAddress();
-        userAddress.setAddresses(user.getAddresses());
         Map<String, Set<Address>> addressByRegion = new HashMap<>();
         for (Address address : user.getAddresses()) {
-            Set<Address> addresses = addressByRegion.get(address.getState());
+            Set<Address> addresses = Optional.ofNullable(addressByRegion.get(address.getState()))
-            if (addresses == null)
+                .orElse(new HashSet<>());
-                addresses = new HashSet<>();
             addresses.add(address);
             addressByRegion.put(address.getState(), addresses);
         }
         userAddress.setAddressByRegion(addressByRegion);
         readRepository.addUserAddress(user.getUserid(), userAddress);
-
     }
-
 }

java-es-cqrs/src/main/java/com/baeldung/patterns/crud/Main.java

@@ -1,48 +0,0 @@
-package com.baeldung.patterns.crud;
-
-import java.util.UUID;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
-
-import com.baeldung.patterns.crud.repository.UserRepository;
-import com.baeldung.patterns.crud.service.UserService;
-import com.baeldung.patterns.domain.Address;
-import com.baeldung.patterns.domain.Contact;
-
-public class Main {
-
-    public static void main(String[] args) throws Exception {
-
-        UserRepository repository = new UserRepository();
-        UserService service = new UserService(repository);
-        String userId = UUID.randomUUID()
-            .toString();
-
-        service.createUser(userId, "Tom", "Sawyer");
-        service.updateUser(userId, 
-            Stream.of(
-              new Contact("EMAIL", "tom.sawyer@gmail.com"), 
-              new Contact("EMAIL", "tom.sawyer@rediff.com"), 
-              new Contact("PHONE", "700-000-0001"))
-            .collect(Collectors.toSet()),
-            Stream.of(
-              new Address("New York", "NY", "10001"), 
-              new Address("Los Angeles", "CA", "90001"), 
-              new Address("Housten", "TX", "77001"))
-            .collect(Collectors.toSet()));
-        service.updateUser(userId, 
-            Stream.of(
-              new Contact("EMAIL", "tom.sawyer@gmail.com"), 
-              new Contact("PHONE", "700-000-0001"))
-            .collect(Collectors.toSet()),
-            Stream.of(
-              new Address("New York", "NY", "10001"), 
-              new Address("Housten", "TX", "77001"))
-            .collect(Collectors.toSet()));
-
-        System.out.println(service.getContactByType(userId, "EMAIL"));
-        System.out.println(service.getAddressByRegion(userId, "NY"));
-
-    }
-
-}

java-es-cqrs/src/main/java/com/baeldung/patterns/domain/UserAddress.java

@@ -1,7 +1,6 @@
 package com.baeldung.patterns.domain;
 
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
@@ -10,7 +9,6 @@ import lombok.Data;
 @Data
 public class UserAddress {
 
-    private Set<Address> addresses = new HashSet<>();
     private Map<String, Set<Address>> addressByRegion = new HashMap<>();
 
 }

java-es-cqrs/src/main/java/com/baeldung/patterns/domain/UserContact.java

@@ -1,7 +1,6 @@
 package com.baeldung.patterns.domain;
 
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
@@ -10,7 +9,6 @@ import lombok.Data;
 @Data
 public class UserContact {
 
-    private Set<Contact> contacts = new HashSet<>();
     private Map<String, Set<Contact>> contactByType = new HashMap<>();
 
 }

java-es-cqrs/src/main/java/com/baeldung/patterns/es/Main.java

@@ -1,48 +0,0 @@
-package com.baeldung.patterns.es;
-
-import java.util.UUID;
-import java.util.stream.Collectors;
-import java.util.stream.Stream;
-
-import com.baeldung.patterns.domain.Address;
-import com.baeldung.patterns.domain.Contact;
-import com.baeldung.patterns.es.repository.EventStore;
-import com.baeldung.patterns.es.service.UserService;
-
-public class Main {
-
-    public static void main(String[] args) throws Exception {
-
-        EventStore repository = new EventStore();
-        UserService service = new UserService(repository);
-        String userId = UUID.randomUUID()
-            .toString();
-
-        service.createUser(userId, "Tom", "Sawyer");
-        service.updateUser(userId, 
-            Stream.of(
-              new Contact("EMAIL", "tom.sawyer@gmail.com"), 
-              new Contact("EMAIL", "tom.sawyer@rediff.com"), 
-              new Contact("PHONE", "700-000-0001"))
-            .collect(Collectors.toSet()),
-            Stream.of(
-              new Address("New York", "NY", "10001"), 
-              new Address("Los Angeles", "CA", "90001"), 
-              new Address("Housten", "TX", "77001"))
-            .collect(Collectors.toSet()));
-        service.updateUser(userId, 
-            Stream.of(
-              new Contact("EMAIL", "tom.sawyer@gmail.com"), 
-              new Contact("PHONE", "700-000-0001"))
-            .collect(Collectors.toSet()),
-            Stream.of(
-              new Address("New York", "NY", "10001"), 
-              new Address("Housten", "TX", "77001"))
-            .collect(Collectors.toSet()));
-
-        System.out.println(service.getContactByType(userId, "EMAIL"));
-        System.out.println(service.getAddressByRegion(userId, "NY"));
-
-    }
-
-}

java-es-cqrs/src/main/java/com/baeldung/patterns/es/events/UserRemovedEvent.java

@@ -1,12 +0,0 @@
-package com.baeldung.patterns.es.events;
-
-import lombok.AllArgsConstructor;
-import lombok.Data;
-import lombok.EqualsAndHashCode;
-
-@Data
-@AllArgsConstructor
-@EqualsAndHashCode(callSuper = false)
-public class UserRemovedEvent extends Event {
-
-}

java-es-cqrs/src/main/java/com/baeldung/patterns/es/service/UserService.java

@@ -1,6 +1,5 @@
 package com.baeldung.patterns.es.service;
 
-import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 
@@ -23,8 +22,7 @@ public class UserService {
     }
 
     public void createUser(String userId, String firstName, String lastName) {
-        UserCreatedEvent event = new UserCreatedEvent(userId, firstName, lastName);
+        repository.addEvent(userId, new UserCreatedEvent(userId, firstName, lastName));
-        repository.addEvent(userId, event);
     }
 
     public void updateUser(String userId, Set<Contact> contacts, Set<Address> addresses) throws Exception {
@@ -32,49 +30,30 @@ public class UserService {
         if (user == null)
             throw new Exception("User does not exist.");
 
-        List<Contact> contactsToRemove = user.getContacts()
+        user.getContacts()
             .stream()
             .filter(c -> !contacts.contains(c))
-            .collect(Collectors.toList());
+            .forEach(c -> repository.addEvent(userId, new UserContactRemovedEvent(c.getType(), c.getDetail())));
-        for (Contact contact : contactsToRemove) {
+        contacts.stream()
-            UserContactRemovedEvent contactRemovedEvent = new UserContactRemovedEvent(contact.getType(), contact.getDetail());
-            repository.addEvent(userId, contactRemovedEvent);
-        }
-
-        List<Contact> contactsToAdd = contacts.stream()
             .filter(c -> !user.getContacts()
                 .contains(c))
-            .collect(Collectors.toList());
+            .forEach(c -> repository.addEvent(userId, new UserContactAddedEvent(c.getType(), c.getDetail())));
-        for (Contact contact : contactsToAdd) {
+        user.getAddresses()
-            UserContactAddedEvent contactAddedEvent = new UserContactAddedEvent(contact.getType(), contact.getDetail());
-            repository.addEvent(userId, contactAddedEvent);
-        }
-
-        List<Address> addressesToRemove = user.getAddresses()
             .stream()
             .filter(a -> !addresses.contains(a))
-            .collect(Collectors.toList());
+            .forEach(a -> repository.addEvent(userId, new UserAddressRemovedEvent(a.getCity(), a.getState(), a.getPostcode())));
-        for (Address address : addressesToRemove) {
+        addresses.stream()
-            UserAddressRemovedEvent addressRemovedEvent = new UserAddressRemovedEvent(address.getCity(), address.getState(), address.getPostcode());
-            repository.addEvent(userId, addressRemovedEvent);
-        }
-
-        List<Address> addressesToAdd = addresses.stream()
             .filter(a -> !user.getAddresses()
                 .contains(a))
-            .collect(Collectors.toList());
+            .forEach(a -> repository.addEvent(userId, new UserAddressAddedEvent(a.getCity(), a.getState(), a.getPostcode())));
-        for (Address address : addressesToAdd) {
-            UserAddressAddedEvent addressAddedEvent = new UserAddressAddedEvent(address.getCity(), address.getState(), address.getPostcode());
-            repository.addEvent(userId, addressAddedEvent);
-        }
     }
 
     public Set<Contact> getContactByType(String userId, String contactType) throws Exception {
         User user = UserUtility.recreateUserState(repository, userId);
         if (user == null)
             throw new Exception("User does not exist.");
-        Set<Contact> contacts = user.getContacts();
+        return user.getContacts()
-        return contacts.stream()
+            .stream()
             .filter(c -> c.getType()
                 .equals(contactType))
             .collect(Collectors.toSet());
@@ -84,11 +63,10 @@ public class UserService {
         User user = UserUtility.recreateUserState(repository, userId);
         if (user == null)
             throw new Exception("User does not exist.");
-        Set<Address> addresses = user.getAddresses();
+        return user.getAddresses()
-        return addresses.stream()
+            .stream()
             .filter(a -> a.getState()
                 .equals(state))
             .collect(Collectors.toSet());
     }
-
 }

java-es-cqrs/src/main/java/com/baeldung/patterns/es/service/UserUtility.java

@@ -12,7 +12,6 @@ import com.baeldung.patterns.es.events.UserAddressRemovedEvent;
 import com.baeldung.patterns.es.events.UserContactAddedEvent;
 import com.baeldung.patterns.es.events.UserContactRemovedEvent;
 import com.baeldung.patterns.es.events.UserCreatedEvent;
-import com.baeldung.patterns.es.events.UserRemovedEvent;
 import com.baeldung.patterns.es.repository.EventStore;
 
 public class UserUtility {
@@ -27,9 +26,6 @@ public class UserUtility {
                 user = new User(UUID.randomUUID()
                     .toString(), e.getFirstName(), e.getLastName());
             }
-            if (event instanceof UserRemovedEvent) {
-                user = null;
-            }
             if (event instanceof UserAddressAddedEvent) {
                 UserAddressAddedEvent e = (UserAddressAddedEvent) event;
                 Address address = new Address(e.getCity(), e.getState(), e.getPostCode());

java-es-cqrs/src/main/java/com/baeldung/patterns/escqrs/projectors/UserProjector.java

@@ -2,6 +2,7 @@ package com.baeldung.patterns.escqrs.projectors;
 
 import java.util.HashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 
 import com.baeldung.patterns.cqrs.repository.UserReadRepository;
@@ -14,8 +15,6 @@ import com.baeldung.patterns.es.events.UserAddressAddedEvent;
 import com.baeldung.patterns.es.events.UserAddressRemovedEvent;
 import com.baeldung.patterns.es.events.UserContactAddedEvent;
 import com.baeldung.patterns.es.events.UserContactRemovedEvent;
-import com.baeldung.patterns.es.events.UserCreatedEvent;
-import com.baeldung.patterns.es.events.UserRemovedEvent;
 
 public class UserProjector {
 
@@ -28,10 +27,6 @@ public class UserProjector {
     public void project(String userId, List<Event> events) {
 
         for (Event event : events) {
-            if (event instanceof UserCreatedEvent)
-                apply(userId, (UserCreatedEvent) event);
-            if (event instanceof UserRemovedEvent)
-                apply(userId, (UserRemovedEvent) event);
             if (event instanceof UserAddressAddedEvent)
                 apply(userId, (UserAddressAddedEvent) event);
             if (event instanceof UserAddressRemovedEvent)
@@ -44,25 +39,13 @@ public class UserProjector {
 
     }
 
-    public void apply(String userId, UserCreatedEvent event) {
-
-    }
-
-    public void apply(String userId, UserRemovedEvent event) {
-
-    }
-
     public void apply(String userId, UserAddressAddedEvent event) {
         Address address = new Address(event.getCity(), event.getState(), event.getPostCode());
-        UserAddress userAddress = readRepository.getUserAddress(userId);
+        UserAddress userAddress = Optional.ofNullable(readRepository.getUserAddress(userId))
-        if (userAddress == null)
+            .orElse(new UserAddress());
-            userAddress = new UserAddress();
+        Set<Address> addresses = Optional.ofNullable(userAddress.getAddressByRegion()
-        userAddress.getAddresses()
+            .get(address.getState()))
-            .add(address);
+            .orElse(new HashSet<>());
-        Set<Address> addresses = userAddress.getAddressByRegion()
-            .get(address.getState());
-        if (addresses == null)
-            addresses = new HashSet<>();
         addresses.add(address);
         userAddress.getAddressByRegion()
             .put(address.getState(), addresses);
@@ -73,30 +56,21 @@ public class UserProjector {
         Address address = new Address(event.getCity(), event.getState(), event.getPostCode());
         UserAddress userAddress = readRepository.getUserAddress(userId);
         if (userAddress != null) {
-            userAddress.getAddresses()
-                .remove(address);
             Set<Address> addresses = userAddress.getAddressByRegion()
                 .get(address.getState());
-            if (addresses != null) {
+            if (addresses != null)
                 addresses.remove(address);
-                userAddress.getAddressByRegion()
-                    .put(address.getState(), addresses);
-            }
             readRepository.addUserAddress(userId, userAddress);
         }
     }
 
     public void apply(String userId, UserContactAddedEvent event) {
         Contact contact = new Contact(event.getContactType(), event.getContactDetails());
-        UserContact userContact = readRepository.getUserContact(userId);
+        UserContact userContact = Optional.ofNullable(readRepository.getUserContact(userId))
-        if (userContact == null)
+            .orElse(new UserContact());
-            userContact = new UserContact();
+        Set<Contact> contacts = Optional.ofNullable(userContact.getContactByType()
-        userContact.getContacts()
+            .get(contact.getType()))
-            .add(contact);
+            .orElse(new HashSet<>());
-        Set<Contact> contacts = userContact.getContactByType()
-            .get(contact.getType());
-        if (contacts == null)
-            contacts = new HashSet<>();
         contacts.add(contact);
         userContact.getContactByType()
             .put(contact.getType(), contacts);
@@ -107,17 +81,11 @@ public class UserProjector {
         Contact contact = new Contact(event.getContactType(), event.getContactDetails());
         UserContact userContact = readRepository.getUserContact(userId);
         if (userContact != null) {
-            userContact.getContacts()
-                .remove(contact);
             Set<Contact> contacts = userContact.getContactByType()
                 .get(contact.getType());
-            if (contacts != null) {
+            if (contacts != null)
                 contacts.remove(contact);
-                userContact.getContactByType()
-                    .put(contact.getType(), contacts);
-            }
             readRepository.addUserContact(userId, userContact);
         }
     }
-
 }

java-es-cqrs/src/test/java/com/baeldung/patterns/cqrs/ApplicationUnitTest.java

@@ -1,9 +1,14 @@
 package com.baeldung.patterns.cqrs;
 
+import static org.junit.Assert.assertEquals;
+
 import java.util.UUID;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.junit.Before;
+import org.junit.Test;
+
 import com.baeldung.patterns.cqrs.aggregates.UserAggregate;
 import com.baeldung.patterns.cqrs.commands.CreateUserCommand;
 import com.baeldung.patterns.cqrs.commands.UpdateUserCommand;
@@ -17,15 +22,25 @@ import com.baeldung.patterns.domain.Address;
 import com.baeldung.patterns.domain.Contact;
 import com.baeldung.patterns.domain.User;
 
-public class Main {
+public class ApplicationUnitTest {
 
-    public static void main(String[] args) throws Exception {
+    private UserWriteRepository writeRepository;
-        UserWriteRepository writeRepository = new UserWriteRepository();
+    private UserReadRepository readRepository;
-        UserReadRepository readRepository = new UserReadRepository();
+    private UserProjector projector;
-        UserProjector projector = new UserProjector(readRepository);
+    private UserAggregate userAggregate;
-        UserAggregate userAggregate = new UserAggregate(writeRepository);
+    private UserProjection userProjection;
-        UserProjection userProjection = new UserProjection(readRepository);
 
+    @Before
+    public void setUp() {
+        writeRepository = new UserWriteRepository();
+        readRepository = new UserReadRepository();
+        projector = new UserProjector(readRepository);
+        userAggregate = new UserAggregate(writeRepository);
+        userProjection = new UserProjection(readRepository);
+    }
+
+    @Test
+    public void testApplication() throws Exception {
         String userId = UUID.randomUUID()
             .toString();
         User user = null;
@@ -47,11 +62,13 @@ public class Main {
         user = userAggregate.handleUpdateUserCommand(updateUserCommand);
         projector.project(user);
 
-        AddressByRegionQuery addressByRegionQuery = new AddressByRegionQuery(user.getUserid(), "NY");
+        ContactByTypeQuery contactByTypeQuery = new ContactByTypeQuery(userId, "EMAIL");
-        System.out.println(userProjection.handle(addressByRegionQuery));
+        assertEquals(Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"))
+            .collect(Collectors.toSet()), userProjection.handle(contactByTypeQuery));
+        AddressByRegionQuery addressByRegionQuery = new AddressByRegionQuery(userId, "NY");
+        assertEquals(Stream.of(new Address("New York", "NY", "10001"))
+            .collect(Collectors.toSet()), userProjection.handle(addressByRegionQuery));
 
-        ContactByTypeQuery contactByTypeQuery = new ContactByTypeQuery(user.getUserid(), "EMAIL");
-        System.out.println(userProjection.handle(contactByTypeQuery));
     }
 
 }

java-es-cqrs/src/test/java/com/baeldung/patterns/crud/ApplicationUnitTest.java

@@ -0,0 +1,48 @@
+package com.baeldung.patterns.crud;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.UUID;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.patterns.crud.repository.UserRepository;
+import com.baeldung.patterns.crud.service.UserService;
+import com.baeldung.patterns.domain.Address;
+import com.baeldung.patterns.domain.Contact;
+
+public class ApplicationUnitTest {
+
+    private UserRepository repository;
+
+    @Before
+    public void setUp() {
+        repository = new UserRepository();
+    }
+
+    @Test
+    public void testApplication() throws Exception {
+        UserService service = new UserService(repository);
+        String userId = UUID.randomUUID()
+            .toString();
+
+        service.createUser(userId, "Tom", "Sawyer");
+        service.updateUser(userId, Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"), new Contact("EMAIL", "tom.sawyer@rediff.com"), new Contact("PHONE", "700-000-0001"))
+            .collect(Collectors.toSet()),
+            Stream.of(new Address("New York", "NY", "10001"), new Address("Los Angeles", "CA", "90001"), new Address("Housten", "TX", "77001"))
+                .collect(Collectors.toSet()));
+        service.updateUser(userId, Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"), new Contact("PHONE", "700-000-0001"))
+            .collect(Collectors.toSet()),
+            Stream.of(new Address("New York", "NY", "10001"), new Address("Housten", "TX", "77001"))
+                .collect(Collectors.toSet()));
+
+        assertEquals(Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"))
+            .collect(Collectors.toSet()), service.getContactByType(userId, "EMAIL"));
+        assertEquals(Stream.of(new Address("New York", "NY", "10001"))
+            .collect(Collectors.toSet()), service.getAddressByRegion(userId, "NY"));
+    }
+
+}

java-es-cqrs/src/test/java/com/baeldung/patterns/es/ApplicationUnitTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.patterns.es;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.UUID;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.baeldung.patterns.domain.Address;
+import com.baeldung.patterns.domain.Contact;
+import com.baeldung.patterns.es.repository.EventStore;
+import com.baeldung.patterns.es.service.UserService;
+
+public class ApplicationUnitTest {
+
+    private EventStore repository;
+    private UserService service;
+
+    @Before
+    public void setUp() {
+        repository = new EventStore();
+        service = new UserService(repository);
+    }
+
+    @Test
+    public void testApplication() throws Exception {
+        String userId = UUID.randomUUID()
+            .toString();
+
+        service.createUser(userId, "Tom", "Sawyer");
+        service.updateUser(userId, Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"), new Contact("EMAIL", "tom.sawyer@rediff.com"), new Contact("PHONE", "700-000-0001"))
+            .collect(Collectors.toSet()),
+            Stream.of(new Address("New York", "NY", "10001"), new Address("Los Angeles", "CA", "90001"), new Address("Housten", "TX", "77001"))
+                .collect(Collectors.toSet()));
+        service.updateUser(userId, Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"), new Contact("PHONE", "700-000-0001"))
+            .collect(Collectors.toSet()),
+            Stream.of(new Address("New York", "NY", "10001"), new Address("Housten", "TX", "77001"))
+                .collect(Collectors.toSet()));
+
+        assertEquals(Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"))
+            .collect(Collectors.toSet()), service.getContactByType(userId, "EMAIL"));
+        assertEquals(Stream.of(new Address("New York", "NY", "10001"))
+            .collect(Collectors.toSet()), service.getAddressByRegion(userId, "NY"));
+
+    }
+
+}

java-es-cqrs/src/test/java/com/baeldung/patterns/escqrs/ApplicationUnitTest.java

@@ -1,10 +1,15 @@
 package com.baeldung.patterns.escqrs;
 
+import static org.junit.Assert.assertEquals;
+
 import java.util.List;
 import java.util.UUID;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.junit.Before;
+import org.junit.Test;
+
 import com.baeldung.patterns.cqrs.commands.CreateUserCommand;
 import com.baeldung.patterns.cqrs.commands.UpdateUserCommand;
 import com.baeldung.patterns.cqrs.projections.UserProjection;
@@ -18,16 +23,25 @@ import com.baeldung.patterns.es.repository.EventStore;
 import com.baeldung.patterns.escqrs.aggregates.UserAggregate;
 import com.baeldung.patterns.escqrs.projectors.UserProjector;
 
-public class Main {
+public class ApplicationUnitTest {
 
-    public static void main(String[] args) throws Exception {
+    private EventStore writeRepository;
+    private UserReadRepository readRepository;
+    private UserProjector projector;
+    private UserAggregate userAggregate;
+    private UserProjection userProjection;
 
-        EventStore writeRepository = new EventStore();
+    @Before
-        UserReadRepository readRepository = new UserReadRepository();
+    public void setUp() {
-        UserProjector projector = new UserProjector(readRepository);
+        writeRepository = new EventStore();
-        UserAggregate userAggregate = new UserAggregate(writeRepository);
+        readRepository = new UserReadRepository();
-        UserProjection userProjection = new UserProjection(readRepository);
+        projector = new UserProjector(readRepository);
+        userAggregate = new UserAggregate(writeRepository);
+        userProjection = new UserProjection(readRepository);
+    }
 
+    @Test
+    public void testApplication() throws Exception {
         String userId = UUID.randomUUID()
             .toString();
         List<Event> events = null;
@@ -50,11 +64,12 @@ public class Main {
         events = userAggregate.handleUpdateUserCommand(updateUserCommand);
         projector.project(userId, events);
 
-        AddressByRegionQuery addressByRegionQuery = new AddressByRegionQuery(userId, "NY");
-        System.out.println(userProjection.handle(addressByRegionQuery));
-
         ContactByTypeQuery contactByTypeQuery = new ContactByTypeQuery(userId, "EMAIL");
-        System.out.println(userProjection.handle(contactByTypeQuery));
+        assertEquals(Stream.of(new Contact("EMAIL", "tom.sawyer@gmail.com"))
+            .collect(Collectors.toSet()), userProjection.handle(contactByTypeQuery));
+        AddressByRegionQuery addressByRegionQuery = new AddressByRegionQuery(userId, "NY");
+        assertEquals(Stream.of(new Address("New York", "NY", "10001"))
+            .collect(Collectors.toSet()), userProjection.handle(addressByRegionQuery));
 
     }