Fix UserService and UserServiceTest

src/Server/src/main/java/greenify/server/service/UserService.java

@@ -27,7 +27,8 @@ public class UserService {
     public UserDto registerUser(String name, String password) {
         User user = userRepository.findByName(name);
         if (user == null) {
-            user = userRepository.save(new User(null, name, password, 0));
+            user = new User(null, name, password, 0);
+            userRepository.save(user);
         } else {
             throw new ApplicationException("User already exists");
         }

src/Server/src/test/java/greenify/server/service/UserServiceTest.java

@@ -11,6 +11,7 @@ import greenify.server.data.repository.UserRepository;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.mockito.Mock;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.test.context.TestConfiguration;
 import org.springframework.boot.test.mock.mockito.MockBean;
@@ -51,6 +52,13 @@ public class UserServiceTest {
         assertEquals(found.getName(), name);
     }
 
+    @Test
+    public void userRegisterTest() {
+        User user = new User(1L, "name", "password", 0);
+        UserDto registered = userService.registerUser(user.getName(), user.getPassword());
+        assertEquals(registered.getName(), "name");
+    }
+
     @Test
     public void getAllUserTest() {
         assertEquals(userRepository.findAll(), userService.getAllUsers());