diff --git a/backend/internal/services/admin_service_test.go b/backend/internal/services/admin_service_test.go
new file mode 100644
index 0000000..4c5e149
--- /dev/null
+++ b/backend/internal/services/admin_service_test.go
@@ -0,0 +1,183 @@
+package services
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+)
+
+func TestAdminService_ListCompanies(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewAdminService(db)
+	ctx := context.Background()
+
+	t.Run("returns empty list when no companies", func(t *testing.T) {
+		// Count query
+		mock.ExpectQuery("SELECT COUNT").WillReturnRows(sqlmock.NewRows([]string{"count"}).AddRow(0))
+		// Data query
+		mock.ExpectQuery("SELECT id, name, slug").WillReturnRows(sqlmock.NewRows([]string{
+			"id", "name", "slug", "type", "document", "address", "region_id", "city_id",
+			"phone", "email", "website", "logo_url", "description", "active", "verified",
+			"created_at", "updated_at",
+		}))
+
+		companies, total, err := service.ListCompanies(ctx, nil, 1, 10)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if total != 0 {
+			t.Errorf("Expected total=0, got %d", total)
+		}
+		if len(companies) != 0 {
+			t.Errorf("Expected 0 companies, got %d", len(companies))
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+
+	t.Run("filters by verified status", func(t *testing.T) {
+		verified := true
+		mock.ExpectQuery("SELECT COUNT").WithArgs(verified).WillReturnRows(sqlmock.NewRows([]string{"count"}).AddRow(0))
+		mock.ExpectQuery("SELECT id, name, slug").WithArgs(verified, 10, 0).WillReturnRows(sqlmock.NewRows([]string{
+			"id", "name", "slug", "type", "document", "address", "region_id", "city_id",
+			"phone", "email", "website", "logo_url", "description", "active", "verified",
+			"created_at", "updated_at",
+		}))
+
+		_, _, err := service.ListCompanies(ctx, &verified, 1, 10)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
+
+func TestAdminService_ListTags(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewAdminService(db)
+	ctx := context.Background()
+
+	t.Run("returns empty list when no tags", func(t *testing.T) {
+		mock.ExpectQuery("SELECT id, name, category, active, created_at, updated_at FROM job_tags").
+			WillReturnRows(sqlmock.NewRows([]string{"id", "name", "category", "active", "created_at", "updated_at"}))
+
+		tags, err := service.ListTags(ctx, nil)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if len(tags) != 0 {
+			t.Errorf("Expected 0 tags, got %d", len(tags))
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+
+	t.Run("filters by category", func(t *testing.T) {
+		category := "stack"
+		mock.ExpectQuery("SELECT id, name, category, active, created_at, updated_at FROM job_tags WHERE category").
+			WithArgs(category).
+			WillReturnRows(sqlmock.NewRows([]string{"id", "name", "category", "active", "created_at", "updated_at"}))
+
+		_, err := service.ListTags(ctx, &category)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
+
+func TestAdminService_CreateTag(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewAdminService(db)
+	ctx := context.Background()
+
+	t.Run("creates a new tag", func(t *testing.T) {
+		mock.ExpectQuery("INSERT INTO job_tags").
+			WithArgs("Go", "stack", true, sqlmock.AnyArg(), sqlmock.AnyArg()).
+			WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow(1))
+
+		tag, err := service.CreateTag(ctx, "Go", "stack")
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if tag == nil {
+			t.Fatal("Expected tag, got nil")
+		}
+		if tag.Name != "Go" {
+			t.Errorf("Expected name='Go', got '%s'", tag.Name)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+
+	t.Run("rejects empty tag name", func(t *testing.T) {
+		_, err := service.CreateTag(ctx, "   ", "stack")
+		if err == nil {
+			t.Error("Expected error for empty tag name")
+		}
+	})
+}
+
+func TestAdminService_GetUser(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewAdminService(db)
+	ctx := context.Background()
+
+	t.Run("returns user by id", func(t *testing.T) {
+		userID := "019b5290-9680-7c06-9ee3-c9e0e117251b"
+		now := time.Now()
+		mock.ExpectQuery("SELECT id, name, email, role, created_at FROM users WHERE id").
+			WithArgs(userID).
+			WillReturnRows(sqlmock.NewRows([]string{"id", "name", "email", "role", "created_at"}).
+				AddRow(userID, "Test User", "test@example.com", "admin", now))
+
+		user, err := service.GetUser(ctx, userID)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if user == nil {
+			t.Fatal("Expected user, got nil")
+		}
+		if user.Name != "Test User" {
+			t.Errorf("Expected name='Test User', got '%s'", user.Name)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
diff --git a/backend/internal/services/audit_service_test.go b/backend/internal/services/audit_service_test.go
new file mode 100644
index 0000000..9e0106f
--- /dev/null
+++ b/backend/internal/services/audit_service_test.go
@@ -0,0 +1,108 @@
+package services
+
+import (
+	"context"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+)
+
+func TestAuditService_RecordLogin(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewAuditService(db)
+	ctx := context.Background()
+
+	t.Run("records login successfully", func(t *testing.T) {
+		ipAddress := "192.168.1.1"
+		userAgent := "Mozilla/5.0"
+
+		mock.ExpectExec("INSERT INTO login_audit").
+			WithArgs("user-123", "test@example.com", "admin,recruiter", &ipAddress, &userAgent).
+			WillReturnResult(sqlmock.NewResult(1, 1))
+
+		err := service.RecordLogin(ctx, LoginAuditInput{
+			UserID:     "user-123",
+			Identifier: "test@example.com",
+			Roles:      []string{"admin", "recruiter"},
+			IPAddress:  &ipAddress,
+			UserAgent:  &userAgent,
+		})
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+
+	t.Run("records login without optional fields", func(t *testing.T) {
+		mock.ExpectExec("INSERT INTO login_audit").
+			WithArgs("user-456", "admin@test.com", "superadmin", nil, nil).
+			WillReturnResult(sqlmock.NewResult(2, 1))
+
+		err := service.RecordLogin(ctx, LoginAuditInput{
+			UserID:     "user-456",
+			Identifier: "admin@test.com",
+			Roles:      []string{"superadmin"},
+			IPAddress:  nil,
+			UserAgent:  nil,
+		})
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
+
+func TestAuditService_ListLogins(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewAuditService(db)
+	ctx := context.Background()
+
+	t.Run("returns empty list when no audits", func(t *testing.T) {
+		mock.ExpectQuery("SELECT id, user_id, identifier, roles, ip_address, user_agent, created_at FROM login_audit").
+			WithArgs(50).
+			WillReturnRows(sqlmock.NewRows([]string{"id", "user_id", "identifier", "roles", "ip_address", "user_agent", "created_at"}))
+
+		audits, err := service.ListLogins(ctx, 0) // Should default to 50
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if len(audits) != 0 {
+			t.Errorf("Expected 0 audits, got %d", len(audits))
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+
+	t.Run("respects custom limit", func(t *testing.T) {
+		mock.ExpectQuery("SELECT id, user_id, identifier, roles, ip_address, user_agent, created_at FROM login_audit").
+			WithArgs(10).
+			WillReturnRows(sqlmock.NewRows([]string{"id", "user_id", "identifier", "roles", "ip_address", "user_agent", "created_at"}))
+
+		_, err := service.ListLogins(ctx, 10)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
diff --git a/backend/internal/services/notification_service_test.go b/backend/internal/services/notification_service_test.go
new file mode 100644
index 0000000..af85ce2
--- /dev/null
+++ b/backend/internal/services/notification_service_test.go
@@ -0,0 +1,119 @@
+package services
+
+import (
+	"context"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+)
+
+func TestNotificationService_ListNotifications(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewNotificationService(db)
+	ctx := context.Background()
+	userID := "019b5290-9680-7c06-9ee3-c9e0e117251b"
+
+	t.Run("returns empty list when no notifications", func(t *testing.T) {
+		mock.ExpectQuery("SELECT id, user_id, type, title, message, link, read_at, created_at, updated_at FROM notifications").
+			WithArgs(userID).
+			WillReturnRows(sqlmock.NewRows([]string{"id", "user_id", "type", "title", "message", "link", "read_at", "created_at", "updated_at"}))
+
+		notifications, err := service.ListNotifications(ctx, userID)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+		if len(notifications) != 0 {
+			t.Errorf("Expected 0 notifications, got %d", len(notifications))
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
+
+func TestNotificationService_CreateNotification(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewNotificationService(db)
+	ctx := context.Background()
+	userID := "019b5290-9680-7c06-9ee3-c9e0e117251b"
+
+	t.Run("creates a new notification", func(t *testing.T) {
+		mock.ExpectExec("INSERT INTO notifications").
+			WithArgs(userID, "info", "Test Title", "Test message", nil).
+			WillReturnResult(sqlmock.NewResult(1, 1))
+
+		err := service.CreateNotification(ctx, userID, "info", "Test Title", "Test message", nil)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
+
+func TestNotificationService_MarkAsRead(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewNotificationService(db)
+	ctx := context.Background()
+	userID := "019b5290-9680-7c06-9ee3-c9e0e117251b"
+
+	t.Run("marks notification as read", func(t *testing.T) {
+		mock.ExpectExec("UPDATE notifications SET read_at").
+			WithArgs("1", userID).
+			WillReturnResult(sqlmock.NewResult(0, 1))
+
+		err := service.MarkAsRead(ctx, "1", userID)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}
+
+func TestNotificationService_MarkAllAsRead(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Failed to create mock db: %v", err)
+	}
+	defer db.Close()
+
+	service := NewNotificationService(db)
+	ctx := context.Background()
+	userID := "019b5290-9680-7c06-9ee3-c9e0e117251b"
+
+	t.Run("marks all notifications as read", func(t *testing.T) {
+		mock.ExpectExec("UPDATE notifications SET read_at").
+			WithArgs(userID).
+			WillReturnResult(sqlmock.NewResult(0, 5))
+
+		err := service.MarkAllAsRead(ctx, userID)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Errorf("Unmet expectations: %v", err)
+		}
+	})
+}