test(user-service): add unit tests for user service

second-part/hw-03/user-service/src/test/java/com/example/UserServiceTest.java

@@ -0,0 +1,72 @@
+package com.example;
+
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+import static org.mockito.Mockito.when;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class UserServiceTest {
+
+  @Mock private UserDao userDao;
+
+  private UserService userService;
+
+  @BeforeEach
+  void setUp() {
+    userService = new UserService(userDao);
+  }
+
+  @Test
+  void createDelegatesToDao() {
+    User user = new User("User", "user@example.com", 30);
+    when(userDao.create(user)).thenReturn(user);
+
+    User result = userService.create(user);
+
+    assertSame(user, result);
+    verify(userDao).create(user);
+    verifyNoMoreInteractions(userDao);
+  }
+
+  @Test
+  void findByIdDelegatesToDao() {
+    Long id = 1L;
+    User user = new User("User", "user@example.com", 30);
+    when(userDao.findById(id)).thenReturn(user);
+
+    User result = userService.findById(id);
+
+    assertSame(user, result);
+    verify(userDao).findById(id);
+    verifyNoMoreInteractions(userDao);
+  }
+
+  @Test
+  void updateDelegatesToDao() {
+    User user = new User("User", "user@example.com", 30);
+    when(userDao.update(user)).thenReturn(user);
+
+    User result = userService.update(user);
+
+    assertSame(user, result);
+    verify(userDao).update(user);
+    verifyNoMoreInteractions(userDao);
+  }
+
+  @Test
+  void deleteByIdDelegatesToDao() {
+    Long id = 1L;
+
+    userService.deleteById(id);
+
+    verify(userDao).deleteById(id);
+    verifyNoMoreInteractions(userDao);
+  }
+}