diff --git a/walkguide-backend/demo/src/test/java/com/walkguide/service/GeofenceServiceTest.java b/walkguide-backend/demo/src/test/java/com/walkguide/service/GeofenceServiceTest.java
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+++ b/walkguide-backend/demo/src/test/java/com/walkguide/service/GeofenceServiceTest.java
@@ -0,0 +1,184 @@
+package com.walkguide.service;
+
+import com.walkguide.dto.request.GeofenceConfigRequest;
+import com.walkguide.dto.response.GeofenceResponse;
+import com.walkguide.entity.GeofenceConfig;
+import com.walkguide.entity.PairingRelation;
+import com.walkguide.entity.User;
+import com.walkguide.enums.PairingStatus;
+import com.walkguide.exception.PairingException;
+import com.walkguide.repository.GeofenceConfigRepository;
+import com.walkguide.repository.PairingRelationRepository;
+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.*;
+import static org.mockito.Mockito.*;
+
+@ExtendWith(MockitoExtension.class)
+@DisplayName("GeofenceService Unit Tests")
+class GeofenceServiceTest {
+
+    @Mock GeofenceConfigRepository geofenceConfigRepository;
+    @Mock PairingRelationRepository pairingRelationRepository;
+
+    @InjectMocks GeofenceService geofenceService;
+
+    private User guardian;
+    private User user;
+    private PairingRelation activePairing;
+    private GeofenceConfig existingConfig;
+
+    @BeforeEach
+    void setUp() {
+        guardian = User.builder().id(1L).email("guardian@test.com").displayName("Guardian Test").build();
+        user = User.builder().id(2L).email("user@test.com").displayName("User Test").build();
+
+        activePairing = PairingRelation.builder()
+                .id(1L)
+                .guardian(guardian)
+                .user(user)
+                .status(PairingStatus.ACTIVE)
+                .build();
+
+        existingConfig = GeofenceConfig.builder()
+                .id(10L)
+                .userId(2L)
+                .guardianId(1L)
+                .centerLat(-7.257)
+                .centerLng(112.752)
+                .radiusMeters(300.0)
+                .enabled(true)
+                .build();
+    }
+
+    // ===== getConfig TESTS =====
+
+    @Test
+    @DisplayName("getConfig - konfigurasi ada: harus return data dari repository")
+    void getConfig_configExists_shouldReturnExistingConfig() {
+        when(geofenceConfigRepository.findByUserId(2L)).thenReturn(Optional.of(existingConfig));
+
+        GeofenceResponse result = geofenceService.getConfig(2L);
+
+        assertThat(result).isNotNull();
+        assertThat(result.getId()).isEqualTo(10L);
+        assertThat(result.getCenterLat()).isEqualTo(-7.257);
+        assertThat(result.getCenterLng()).isEqualTo(112.752);
+        assertThat(result.getRadiusMeters()).isEqualTo(300.0);
+        assertThat(result.getEnabled()).isTrue();
+    }
+
+    @Test
+    @DisplayName("getConfig - konfigurasi tidak ada: harus return default (disabled, radius 500m)")
+    void getConfig_configNotFound_shouldReturnDefaultResponse() {
+        when(geofenceConfigRepository.findByUserId(99L)).thenReturn(Optional.empty());
+
+        GeofenceResponse result = geofenceService.getConfig(99L);
+
+        assertThat(result).isNotNull();
+        assertThat(result.getEnabled()).isFalse();
+        assertThat(result.getRadiusMeters()).isEqualTo(500.0);
+        assertThat(result.getId()).isNull();
+    }
+
+    // ===== updateConfig TESTS =====
+
+    @Test
+    @DisplayName("updateConfig - pairing aktif, config sudah ada: harus update field yang diberikan saja")
+    void updateConfig_activePairingAndConfigExists_shouldUpdateFields() {
+        GeofenceConfigRequest req = new GeofenceConfigRequest();
+        req.setCenterLat(-7.300);
+        req.setCenterLng(112.800);
+        req.setRadiusMeters(400.0);
+        req.setEnabled(true);
+
+        when(pairingRelationRepository.findByGuardian_IdAndStatus(1L, PairingStatus.ACTIVE))
+                .thenReturn(Optional.of(activePairing));
+        when(geofenceConfigRepository.findByUserId(2L)).thenReturn(Optional.of(existingConfig));
+        when(geofenceConfigRepository.save(any(GeofenceConfig.class))).thenAnswer(inv -> inv.getArgument(0));
+
+        GeofenceResponse result = geofenceService.updateConfig(1L, req);
+
+        assertThat(result).isNotNull();
+        assertThat(result.getCenterLat()).isEqualTo(-7.300);
+        assertThat(result.getCenterLng()).isEqualTo(112.800);
+        assertThat(result.getRadiusMeters()).isEqualTo(400.0);
+        assertThat(result.getEnabled()).isTrue();
+        verify(geofenceConfigRepository).save(any(GeofenceConfig.class));
+    }
+
+    @Test
+    @DisplayName("updateConfig - config belum ada: harus buat config baru dengan userId dari pairing")
+    void updateConfig_configNotExists_shouldCreateNewConfig() {
+        GeofenceConfigRequest req = new GeofenceConfigRequest();
+        req.setCenterLat(-7.100);
+        req.setCenterLng(112.600);
+        req.setRadiusMeters(200.0);
+        req.setEnabled(false);
+
+        when(pairingRelationRepository.findByGuardian_IdAndStatus(1L, PairingStatus.ACTIVE))
+                .thenReturn(Optional.of(activePairing));
+        when(geofenceConfigRepository.findByUserId(2L)).thenReturn(Optional.empty());
+        when(geofenceConfigRepository.save(any(GeofenceConfig.class))).thenAnswer(inv -> {
+            GeofenceConfig saved = inv.getArgument(0);
+            saved.setId(20L);
+            return saved;
+        });
+
+        GeofenceResponse result = geofenceService.updateConfig(1L, req);
+
+        ArgumentCaptor<GeofenceConfig> captor = ArgumentCaptor.forClass(GeofenceConfig.class);
+        verify(geofenceConfigRepository).save(captor.capture());
+        GeofenceConfig saved = captor.getValue();
+        assertThat(saved.getUserId()).isEqualTo(2L);
+        assertThat(saved.getGuardianId()).isEqualTo(1L);
+        assertThat(result.getCenterLat()).isEqualTo(-7.100);
+        assertThat(result.getEnabled()).isFalse();
+    }
+
+    @Test
+    @DisplayName("updateConfig - request field null: harus tidak menimpa nilai yang sudah ada")
+    void updateConfig_partialRequest_shouldNotOverwriteNullFields() {
+        GeofenceConfigRequest req = new GeofenceConfigRequest();
+        req.setEnabled(false); // hanya ubah enabled, field lain null
+
+        when(pairingRelationRepository.findByGuardian_IdAndStatus(1L, PairingStatus.ACTIVE))
+                .thenReturn(Optional.of(activePairing));
+        when(geofenceConfigRepository.findByUserId(2L)).thenReturn(Optional.of(existingConfig));
+        when(geofenceConfigRepository.save(any(GeofenceConfig.class))).thenAnswer(inv -> inv.getArgument(0));
+
+        GeofenceResponse result = geofenceService.updateConfig(1L, req);
+
+        // centerLat, centerLng, radiusMeters tidak berubah
+        assertThat(result.getCenterLat()).isEqualTo(-7.257);
+        assertThat(result.getCenterLng()).isEqualTo(112.752);
+        assertThat(result.getRadiusMeters()).isEqualTo(300.0);
+        assertThat(result.getEnabled()).isFalse();
+    }
+
+    @Test
+    @DisplayName("updateConfig - tidak ada pairing aktif: harus throw PairingException")
+    void updateConfig_noActivePairing_shouldThrowPairingException() {
+        GeofenceConfigRequest req = new GeofenceConfigRequest();
+        req.setEnabled(true);
+
+        when(pairingRelationRepository.findByGuardian_IdAndStatus(1L, PairingStatus.ACTIVE))
+                .thenReturn(Optional.empty());
+
+        assertThatThrownBy(() -> geofenceService.updateConfig(1L, req))
+                .isInstanceOf(PairingException.class)
+                .hasMessageContaining("Tidak ada user yang dipair");
+
+        verify(geofenceConfigRepository, never()).save(any());
+    }
+}
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