diff --git a/walkguide-backend/demo/src/test/java/com/walkguide/service/UserSettingServiceTest.java b/walkguide-backend/demo/src/test/java/com/walkguide/service/UserSettingServiceTest.java
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+++ b/walkguide-backend/demo/src/test/java/com/walkguide/service/UserSettingServiceTest.java
@@ -0,0 +1,202 @@
+package com.walkguide.service;
+
+import com.walkguide.dto.request.UserSettingsUpdateRequest;
+import com.walkguide.dto.response.UserSettingsResponse;
+import com.walkguide.entity.UserSettings;
+import com.walkguide.repository.UserSettingsRepository;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.util.Optional;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+@DisplayName("UserSettingsService Unit Tests")
+class UserSettingsServiceTest {
+
+    @Mock
+    UserSettingsRepository userSettingsRepository;
+
+    @InjectMocks
+    UserSettingsService userSettingsService;
+
+    private UserSettings existingSettings;
+
+    @BeforeEach
+    void setUp() {
+        existingSettings = UserSettings.builder()
+                .id(1L)
+                .userId(10L)
+                .ttsLanguage("id-ID")
+                .ttsPitch(1.0)
+                .ttsSpeed(0.9)
+                .warnNoGuardian(true)
+                .hapticEnabled(true)
+                .build();
+    }
+
+    // ===== getSettings TESTS =====
+
+    @Test
+    @DisplayName("getSettings - harus return settings yang ada di DB")
+    void getSettings_existingSettings_shouldReturnExistingData() {
+        when(userSettingsRepository.findByUserId(10L)).thenReturn(Optional.of(existingSettings));
+
+        UserSettingsResponse result = userSettingsService.getSettings(10L);
+
+        assertThat(result).isNotNull();
+        assertThat(result.getId()).isEqualTo(1L);
+        assertThat(result.getTtsLanguage()).isEqualTo("id-ID");
+        assertThat(result.getTtsPitch()).isEqualTo(1.0);
+        assertThat(result.getTtsSpeed()).isEqualTo(0.9);
+        assertThat(result.getWarnNoGuardian()).isTrue();
+        assertThat(result.getHapticEnabled()).isTrue();
+
+        // Tidak boleh membuat settings baru jika sudah ada
+        verify(userSettingsRepository, never()).save(any());
+    }
+
+    @Test
+    @DisplayName("getSettings - jika belum ada, harus auto-create settings default dan simpan ke DB")
+    void getSettings_noExistingSettings_shouldCreateDefaultAndSave() {
+        UserSettings defaultSettings = UserSettings.builder()
+                .id(2L).userId(20L)
+                .ttsLanguage("id-ID").ttsPitch(1.0).ttsSpeed(0.9)
+                .warnNoGuardian(true).hapticEnabled(true).build();
+
+        when(userSettingsRepository.findByUserId(20L)).thenReturn(Optional.empty());
+        when(userSettingsRepository.save(any(UserSettings.class))).thenReturn(defaultSettings);
+
+        UserSettingsResponse result = userSettingsService.getSettings(20L);
+
+        assertThat(result).isNotNull();
+        verify(userSettingsRepository).save(any(UserSettings.class));
+    }
+
+    @Test
+    @DisplayName("getSettings - settings yang di-auto-create harus memiliki userId yang benar")
+    void getSettings_autoCreate_shouldHaveCorrectUserId() {
+        when(userSettingsRepository.findByUserId(30L)).thenReturn(Optional.empty());
+        when(userSettingsRepository.save(any(UserSettings.class)))
+                .thenAnswer(inv -> inv.getArgument(0));
+
+        userSettingsService.getSettings(30L);
+
+        ArgumentCaptor<UserSettings> captor = ArgumentCaptor.forClass(UserSettings.class);
+        verify(userSettingsRepository).save(captor.capture());
+        assertThat(captor.getValue().getUserId()).isEqualTo(30L);
+    }
+
+    // ===== updateSettings TESTS =====
+
+    @Test
+    @DisplayName("updateSettings - semua field diisi harus mengupdate semua nilai")
+    void updateSettings_allFields_shouldUpdateAllValues() {
+        UserSettingsUpdateRequest req = new UserSettingsUpdateRequest();
+        req.setTtsLanguage("en-US");
+        req.setTtsPitch(1.5);
+        req.setTtsSpeed(1.2);
+        req.setWarnNoGuardian(false);
+        req.setHapticEnabled(false);
+
+        when(userSettingsRepository.findByUserId(10L)).thenReturn(Optional.of(existingSettings));
+        when(userSettingsRepository.save(any(UserSettings.class)))
+                .thenAnswer(inv -> inv.getArgument(0));
+
+        UserSettingsResponse result = userSettingsService.updateSettings(10L, req);
+
+        assertThat(result.getTtsLanguage()).isEqualTo("en-US");
+        assertThat(result.getTtsPitch()).isEqualTo(1.5);
+        assertThat(result.getTtsSpeed()).isEqualTo(1.2);
+        assertThat(result.getWarnNoGuardian()).isFalse();
+        assertThat(result.getHapticEnabled()).isFalse();
+    }
+
+    @Test
+    @DisplayName("updateSettings - field null tidak boleh mengubah nilai yang sudah ada (partial update)")
+    void updateSettings_partialUpdate_nullFieldsShouldNotOverride() {
+        UserSettingsUpdateRequest req = new UserSettingsUpdateRequest();
+        req.setTtsLanguage("en-US"); // hanya ini yang diubah
+        req.setTtsPitch(null);
+        req.setTtsSpeed(null);
+        req.setWarnNoGuardian(null);
+        req.setHapticEnabled(null);
+
+        when(userSettingsRepository.findByUserId(10L)).thenReturn(Optional.of(existingSettings));
+        when(userSettingsRepository.save(any(UserSettings.class)))
+                .thenAnswer(inv -> inv.getArgument(0));
+
+        UserSettingsResponse result = userSettingsService.updateSettings(10L, req);
+
+        assertThat(result.getTtsLanguage()).isEqualTo("en-US");
+        // Nilai lama harus tetap
+        assertThat(result.getTtsPitch()).isEqualTo(1.0);
+        assertThat(result.getTtsSpeed()).isEqualTo(0.9);
+        assertThat(result.getWarnNoGuardian()).isTrue();
+        assertThat(result.getHapticEnabled()).isTrue();
+    }
+
+    @Test
+    @DisplayName("updateSettings - jika belum ada settings, harus buat baru dan update")
+    void updateSettings_noExistingSettings_shouldCreateNewAndUpdate() {
+        UserSettingsUpdateRequest req = new UserSettingsUpdateRequest();
+        req.setTtsLanguage("ja-JP");
+        req.setHapticEnabled(false);
+
+        when(userSettingsRepository.findByUserId(40L)).thenReturn(Optional.empty());
+        when(userSettingsRepository.save(any(UserSettings.class)))
+                .thenAnswer(inv -> inv.getArgument(0));
+
+        UserSettingsResponse result = userSettingsService.updateSettings(40L, req);
+
+        ArgumentCaptor<UserSettings> captor = ArgumentCaptor.forClass(UserSettings.class);
+        verify(userSettingsRepository).save(captor.capture());
+
+        assertThat(captor.getValue().getUserId()).isEqualTo(40L);
+        assertThat(captor.getValue().getTtsLanguage()).isEqualTo("ja-JP");
+        assertThat(captor.getValue().getHapticEnabled()).isFalse();
+    }
+
+    @Test
+    @DisplayName("updateSettings - harus memanggil repository.save dan return hasil yang diupdate")
+    void updateSettings_shouldPersistAndReturnUpdatedResponse() {
+        UserSettingsUpdateRequest req = new UserSettingsUpdateRequest();
+        req.setTtsSpeed(0.5);
+
+        when(userSettingsRepository.findByUserId(10L)).thenReturn(Optional.of(existingSettings));
+        when(userSettingsRepository.save(any(UserSettings.class)))
+                .thenAnswer(inv -> inv.getArgument(0));
+
+        userSettingsService.updateSettings(10L, req);
+
+        verify(userSettingsRepository, times(1)).save(any(UserSettings.class));
+    }
+
+    @Test
+    @DisplayName("updateSettings - semua field null harus tidak mengubah apapun")
+    void updateSettings_allNull_shouldNotChangeAnything() {
+        UserSettingsUpdateRequest req = new UserSettingsUpdateRequest();
+        // semua null
+
+        when(userSettingsRepository.findByUserId(10L)).thenReturn(Optional.of(existingSettings));
+        when(userSettingsRepository.save(any(UserSettings.class)))
+                .thenAnswer(inv -> inv.getArgument(0));
+
+        UserSettingsResponse result = userSettingsService.updateSettings(10L, req);
+
+        assertThat(result.getTtsLanguage()).isEqualTo("id-ID");
+        assertThat(result.getTtsPitch()).isEqualTo(1.0);
+        assertThat(result.getTtsSpeed()).isEqualTo(0.9);
+        assertThat(result.getWarnNoGuardian()).isTrue();
+        assertThat(result.getHapticEnabled()).isTrue();
+    }
+}
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