added unit test example for registration service

user-registration-application/src/test/java/com/ewolff/user_registration/service/RegistrationServiceUnitTest.java

@@ -0,0 +1,61 @@
+package com.ewolff.user_registration.service;
+
+import com.ewolff.user_registration.domain.User;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.InjectMocks;
+import org.mockito.Matchers;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.jdbc.core.RowMapper;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+import static org.mockito.Matchers.anyObject;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+@RunWith(MockitoJUnitRunner.class)
+public class RegistrationServiceUnitTest {
+
+    @Mock
+    private JdbcTemplate jdbcTemplateMock;
+
+    @InjectMocks
+    private RegistrationService service;
+
+    @Test
+    public void registerNewUser() {
+        // arrange
+        User user = new User("Eberhard","Wolff","eberhard.wolff@gmail.com");
+        // act
+        boolean registered = service.register(user);
+        // assert
+        assertThat(registered, is(true));
+        verify(jdbcTemplateMock).update(
+                anyString(),
+                eq(user.getFirstname()),
+                eq(user.getName()),
+                eq(user.getEmail()));
+    }
+
+    @Test
+    public void doNotRegisterExistingUser() {
+        // arrange
+        User user = new User("Eberhard","Wolff","eberhard.wolff@gmail.com");
+        List<User> users = new ArrayList<>();
+        users.add(user);
+        // simulating that user already exists
+        when(jdbcTemplateMock.query(anyString(), Matchers.any(RowMapper.class), eq(user.getEmail()))).thenReturn(users);
+        // act
+        boolean registered = service.register(user);
+        // assert
+        assertThat("should not register user with existing mail address", registered, is(false));
+    }
+}