diff --git a/jest.config.js b/jest.config.js
index a8eafe4..f1eeae2 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -10,7 +10,6 @@ module.exports = {
   transform: {
     '^.+\\.tsx?$': ['ts-jest', {
       tsconfig: 'tsconfig.json',
-      useESM: true,
       isolatedModules: true,
     }],
   },
@@ -28,5 +27,4 @@ module.exports = {
   setupFilesAfterEnv: ['<rootDir>/src/__tests__/setup.ts'],
   testTimeout: 30000,
   verbose: true,
-  extensionsToTreatAsEsm: ['.ts'],
 };
diff --git a/src/__tests__/core/countries.service.test.ts b/src/__tests__/core/countries.service.test.ts
new file mode 100644
index 0000000..8d7a095
--- /dev/null
+++ b/src/__tests__/core/countries.service.test.ts
@@ -0,0 +1,102 @@
+import { createMockRepository, createMockCountry } from '../helpers';
+import { NotFoundError } from '../../shared/errors';
+
+// Mock the entire module
+const mockRepository = createMockRepository();
+
+jest.mock('../../config/typeorm', () => ({
+  AppDataSource: {
+    getRepository: jest.fn(() => mockRepository),
+  },
+}));
+
+// Import after mocking
+import { countriesService } from '../../modules/core/countries.service';
+
+describe('CountriesService', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('findAll', () => {
+    it('should return all countries ordered by name', async () => {
+      const mockCountries = [
+        createMockCountry({ id: '1', code: 'US', name: 'Estados Unidos' }),
+        createMockCountry({ id: '2', code: 'MX', name: 'México' }),
+      ];
+
+      mockRepository.find.mockResolvedValue(mockCountries);
+
+      const result = await countriesService.findAll();
+
+      expect(mockRepository.find).toHaveBeenCalledWith({
+        order: { name: 'ASC' },
+      });
+      expect(result).toEqual(mockCountries);
+      expect(result).toHaveLength(2);
+    });
+
+    it('should return empty array when no countries exist', async () => {
+      mockRepository.find.mockResolvedValue([]);
+
+      const result = await countriesService.findAll();
+
+      expect(result).toEqual([]);
+      expect(result).toHaveLength(0);
+    });
+  });
+
+  describe('findById', () => {
+    it('should return a country by id', async () => {
+      const mockCountry = createMockCountry({ id: 'country-id-1' });
+      mockRepository.findOne.mockResolvedValue(mockCountry);
+
+      const result = await countriesService.findById('country-id-1');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { id: 'country-id-1' },
+      });
+      expect(result).toEqual(mockCountry);
+    });
+
+    it('should throw NotFoundError when country not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(countriesService.findById('non-existent-id')).rejects.toThrow(NotFoundError);
+    });
+  });
+
+  describe('findByCode', () => {
+    it('should return a country by code', async () => {
+      const mockCountry = createMockCountry({ code: 'MX' });
+      mockRepository.findOne.mockResolvedValue(mockCountry);
+
+      const result = await countriesService.findByCode('MX');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { code: 'MX' },
+      });
+      expect(result).toEqual(mockCountry);
+    });
+
+    it('should return a country by lowercase code (converted to uppercase)', async () => {
+      const mockCountry = createMockCountry({ code: 'MX' });
+      mockRepository.findOne.mockResolvedValue(mockCountry);
+
+      const result = await countriesService.findByCode('mx');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { code: 'MX' },
+      });
+      expect(result).toEqual(mockCountry);
+    });
+
+    it('should return null when country code not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      const result = await countriesService.findByCode('XX');
+
+      expect(result).toBeNull();
+    });
+  });
+});
diff --git a/src/__tests__/core/currencies.service.test.ts b/src/__tests__/core/currencies.service.test.ts
new file mode 100644
index 0000000..38bbed9
--- /dev/null
+++ b/src/__tests__/core/currencies.service.test.ts
@@ -0,0 +1,210 @@
+import { createMockRepository, createMockQueryBuilder, createMockCurrency } from '../helpers';
+import { NotFoundError, ConflictError } from '../../shared/errors';
+
+// Mock the entire module
+const mockRepository = createMockRepository();
+const mockQueryBuilder = createMockQueryBuilder();
+mockRepository.createQueryBuilder.mockReturnValue(mockQueryBuilder);
+
+jest.mock('../../config/typeorm', () => ({
+  AppDataSource: {
+    getRepository: jest.fn(() => mockRepository),
+  },
+}));
+
+// Import after mocking
+import { currenciesService } from '../../modules/core/currencies.service';
+
+describe('CurrenciesService', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+    mockRepository.createQueryBuilder.mockReturnValue(mockQueryBuilder);
+  });
+
+  describe('findAll', () => {
+    it('should return all currencies ordered by code', async () => {
+      const mockCurrencies = [
+        createMockCurrency({ id: '1', code: 'EUR', name: 'Euro' }),
+        createMockCurrency({ id: '2', code: 'MXN', name: 'Peso Mexicano' }),
+        createMockCurrency({ id: '3', code: 'USD', name: 'Dólar Estadounidense' }),
+      ];
+
+      mockQueryBuilder.getMany.mockResolvedValue(mockCurrencies);
+
+      const result = await currenciesService.findAll();
+
+      expect(mockRepository.createQueryBuilder).toHaveBeenCalledWith('currency');
+      expect(mockQueryBuilder.orderBy).toHaveBeenCalledWith('currency.code', 'ASC');
+      expect(result).toEqual(mockCurrencies);
+    });
+
+    it('should filter active currencies when activeOnly is true', async () => {
+      const activeCurrencies = [
+        createMockCurrency({ id: '1', code: 'MXN', active: true }),
+      ];
+
+      mockQueryBuilder.getMany.mockResolvedValue(activeCurrencies);
+
+      const result = await currenciesService.findAll(true);
+
+      expect(mockQueryBuilder.where).toHaveBeenCalledWith('currency.active = :active', { active: true });
+      expect(result).toEqual(activeCurrencies);
+    });
+
+    it('should return all currencies when activeOnly is false', async () => {
+      const allCurrencies = [
+        createMockCurrency({ id: '1', code: 'MXN', active: true }),
+        createMockCurrency({ id: '2', code: 'USD', active: false }),
+      ];
+
+      mockQueryBuilder.getMany.mockResolvedValue(allCurrencies);
+
+      const result = await currenciesService.findAll(false);
+
+      expect(mockQueryBuilder.where).not.toHaveBeenCalled();
+      expect(result).toHaveLength(2);
+    });
+  });
+
+  describe('findById', () => {
+    it('should return a currency by id', async () => {
+      const mockCurrency = createMockCurrency({ id: 'currency-id-1' });
+      mockRepository.findOne.mockResolvedValue(mockCurrency);
+
+      const result = await currenciesService.findById('currency-id-1');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { id: 'currency-id-1' },
+      });
+      expect(result).toEqual(mockCurrency);
+    });
+
+    it('should throw NotFoundError when currency not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(currenciesService.findById('non-existent')).rejects.toThrow(NotFoundError);
+    });
+  });
+
+  describe('findByCode', () => {
+    it('should return a currency by code', async () => {
+      const mockCurrency = createMockCurrency({ code: 'MXN' });
+      mockRepository.findOne.mockResolvedValue(mockCurrency);
+
+      const result = await currenciesService.findByCode('MXN');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { code: 'MXN' },
+      });
+      expect(result).toEqual(mockCurrency);
+    });
+
+    it('should convert lowercase code to uppercase', async () => {
+      const mockCurrency = createMockCurrency({ code: 'USD' });
+      mockRepository.findOne.mockResolvedValue(mockCurrency);
+
+      await currenciesService.findByCode('usd');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { code: 'USD' },
+      });
+    });
+
+    it('should return null when currency not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      const result = await currenciesService.findByCode('XXX');
+
+      expect(result).toBeNull();
+    });
+  });
+
+  describe('create', () => {
+    it('should create a new currency', async () => {
+      const newCurrency = createMockCurrency({ id: 'new-id', code: 'GBP', name: 'Libra Esterlina' });
+      mockRepository.findOne.mockResolvedValue(null); // No existing currency
+      mockRepository.create.mockReturnValue(newCurrency);
+      mockRepository.save.mockResolvedValue(newCurrency);
+
+      const result = await currenciesService.create({
+        code: 'gbp',
+        name: 'Libra Esterlina',
+        symbol: '£',
+      });
+
+      expect(mockRepository.create).toHaveBeenCalledWith({
+        code: 'GBP',
+        name: 'Libra Esterlina',
+        symbol: '£',
+        decimals: 2,
+      });
+      expect(result).toEqual(newCurrency);
+    });
+
+    it('should throw ConflictError when currency code already exists', async () => {
+      const existingCurrency = createMockCurrency({ code: 'MXN' });
+      mockRepository.findOne.mockResolvedValue(existingCurrency);
+
+      await expect(
+        currenciesService.create({
+          code: 'MXN',
+          name: 'Peso Mexicano',
+          symbol: '$',
+        })
+      ).rejects.toThrow(ConflictError);
+    });
+
+    it('should accept decimal_places parameter', async () => {
+      const newCurrency = createMockCurrency({ decimals: 4 });
+      mockRepository.findOne.mockResolvedValue(null);
+      mockRepository.create.mockReturnValue(newCurrency);
+      mockRepository.save.mockResolvedValue(newCurrency);
+
+      await currenciesService.create({
+        code: 'BTC',
+        name: 'Bitcoin',
+        symbol: '₿',
+        decimal_places: 4,
+      });
+
+      expect(mockRepository.create).toHaveBeenCalledWith(
+        expect.objectContaining({ decimals: 4 })
+      );
+    });
+  });
+
+  describe('update', () => {
+    it('should update an existing currency', async () => {
+      const existingCurrency = createMockCurrency({ id: 'currency-id' });
+      const updatedCurrency = { ...existingCurrency, name: 'Updated Name' };
+
+      mockRepository.findOne.mockResolvedValue(existingCurrency);
+      mockRepository.save.mockResolvedValue(updatedCurrency);
+
+      const result = await currenciesService.update('currency-id', { name: 'Updated Name' });
+
+      expect(mockRepository.save).toHaveBeenCalled();
+      expect(result.name).toBe('Updated Name');
+    });
+
+    it('should update active status', async () => {
+      const existingCurrency = createMockCurrency({ id: 'currency-id', active: true });
+      const updatedCurrency = { ...existingCurrency, active: false };
+
+      mockRepository.findOne.mockResolvedValue(existingCurrency);
+      mockRepository.save.mockResolvedValue(updatedCurrency);
+
+      const result = await currenciesService.update('currency-id', { active: false });
+
+      expect(result.active).toBe(false);
+    });
+
+    it('should throw NotFoundError when currency not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(
+        currenciesService.update('non-existent', { name: 'New Name' })
+      ).rejects.toThrow(NotFoundError);
+    });
+  });
+});
diff --git a/src/__tests__/core/states.service.test.ts b/src/__tests__/core/states.service.test.ts
new file mode 100644
index 0000000..7bde38d
--- /dev/null
+++ b/src/__tests__/core/states.service.test.ts
@@ -0,0 +1,151 @@
+import { createMockRepository, createMockQueryBuilder, createMockState, createMockCountry } from '../helpers';
+import { NotFoundError } from '../../shared/errors';
+
+const mockRepository = createMockRepository();
+const mockQueryBuilder = createMockQueryBuilder();
+mockRepository.createQueryBuilder.mockReturnValue(mockQueryBuilder);
+
+const mockCountryRepository = createMockRepository();
+
+jest.mock('../../config/typeorm', () => ({
+  AppDataSource: {
+    getRepository: jest.fn((entity: any) => {
+      if (entity.name === 'Country') return mockCountryRepository;
+      return mockRepository;
+    }),
+  },
+}));
+
+import { statesService } from '../../modules/core/states.service';
+
+describe('StatesService', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+    mockRepository.createQueryBuilder.mockReturnValue(mockQueryBuilder);
+  });
+
+  describe('findAll', () => {
+    it('should return all states with country relation', async () => {
+      const mockStates = [
+        createMockState({ id: '1', code: 'JAL', name: 'Jalisco' }),
+        createMockState({ id: '2', code: 'NLE', name: 'Nuevo León' }),
+      ];
+
+      mockQueryBuilder.getMany.mockResolvedValue(mockStates);
+
+      const result = await statesService.findAll();
+
+      expect(mockRepository.createQueryBuilder).toHaveBeenCalledWith('state');
+      expect(mockQueryBuilder.leftJoinAndSelect).toHaveBeenCalledWith('state.country', 'country');
+      expect(result).toEqual(mockStates);
+    });
+
+    it('should accept filter options', async () => {
+      mockQueryBuilder.getMany.mockResolvedValue([]);
+
+      const result = await statesService.findAll({ active: true });
+
+      expect(result).toEqual([]);
+    });
+  });
+
+  describe('findById', () => {
+    it('should return a state by id', async () => {
+      const mockState = createMockState({ id: 'state-id-1' });
+      mockRepository.findOne.mockResolvedValue(mockState);
+
+      const result = await statesService.findById('state-id-1');
+
+      expect(mockRepository.findOne).toHaveBeenCalledWith({
+        where: { id: 'state-id-1' },
+        relations: ['country'],
+      });
+      expect(result).toEqual(mockState);
+    });
+
+    it('should throw NotFoundError when state not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(statesService.findById('non-existent')).rejects.toThrow(NotFoundError);
+    });
+  });
+
+  describe('findByCountry', () => {
+    it('should return states by country id', async () => {
+      const mockStates = [
+        createMockState({ countryId: 'country-1', code: 'JAL' }),
+      ];
+
+      mockRepository.find.mockResolvedValue(mockStates);
+
+      const result = await statesService.findByCountry('country-1');
+
+      expect(result).toEqual(mockStates);
+    });
+  });
+
+  describe('findByCountryCode', () => {
+    it('should return states filtered by country code', async () => {
+      const mockStates = [createMockState({ countryId: 'country-mx' })];
+      mockQueryBuilder.getMany.mockResolvedValue(mockStates);
+
+      const result = await statesService.findByCountryCode('MX');
+
+      expect(result).toEqual(mockStates);
+    });
+  });
+
+  describe('create', () => {
+    it('should create a new state', async () => {
+      const mockCountry = createMockCountry({ id: 'country-mx' });
+      const newState = createMockState({ id: 'new-state', code: 'AGS', name: 'Aguascalientes' });
+
+      mockCountryRepository.findOne.mockResolvedValue(mockCountry);
+      mockRepository.findOne.mockResolvedValue(null);
+      mockRepository.create.mockReturnValue(newState);
+      mockRepository.save.mockResolvedValue(newState);
+
+      const result = await statesService.create({
+        countryId: 'country-mx',
+        code: 'AGS',
+        name: 'Aguascalientes',
+      });
+
+      expect(result).toEqual(newState);
+    });
+
+    // Note: validation of country existence is tested at the integration level
+  });
+
+  describe('update', () => {
+    it('should update an existing state', async () => {
+      const existingState = createMockState({ id: 'state-id' });
+      const updatedState = { ...existingState, name: 'Updated State' };
+
+      mockRepository.findOne.mockResolvedValue(existingState);
+      mockRepository.save.mockResolvedValue(updatedState);
+
+      const result = await statesService.update('state-id', { name: 'Updated State' });
+
+      expect(result.name).toBe('Updated State');
+    });
+  });
+
+  describe('delete', () => {
+    it('should delete a state', async () => {
+      const existingState = createMockState({ id: 'state-to-delete' });
+      mockRepository.findOne.mockResolvedValue(existingState);
+      mockRepository.remove.mockResolvedValue(existingState);
+
+      await statesService.delete('state-to-delete');
+
+      expect(mockRepository.remove).toHaveBeenCalledWith(existingState);
+    });
+
+    it('should throw NotFoundError when state not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(statesService.delete('non-existent')).rejects.toThrow(NotFoundError);
+    });
+  });
+});
diff --git a/src/__tests__/core/uom.service.test.ts b/src/__tests__/core/uom.service.test.ts
new file mode 100644
index 0000000..307f90e
--- /dev/null
+++ b/src/__tests__/core/uom.service.test.ts
@@ -0,0 +1,218 @@
+import { createMockRepository, createMockQueryBuilder, createMockUom, createMockUomCategory } from '../helpers';
+import { NotFoundError } from '../../shared/errors';
+
+const mockRepository = createMockRepository();
+const mockQueryBuilder = createMockQueryBuilder();
+mockRepository.createQueryBuilder.mockReturnValue(mockQueryBuilder);
+
+const mockCategoryRepository = createMockRepository();
+const mockCategoryQb = createMockQueryBuilder();
+mockCategoryRepository.createQueryBuilder.mockReturnValue(mockCategoryQb);
+
+jest.mock('../../config/typeorm', () => ({
+  AppDataSource: {
+    getRepository: jest.fn((entity: any) => {
+      if (entity.name === 'UomCategory') return mockCategoryRepository;
+      return mockRepository;
+    }),
+  },
+}));
+
+import { uomService } from '../../modules/core/uom.service';
+
+describe('UomService', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+    mockRepository.createQueryBuilder.mockReturnValue(mockQueryBuilder);
+    mockCategoryRepository.createQueryBuilder.mockReturnValue(mockCategoryQb);
+  });
+
+  describe('findAllCategories', () => {
+    it('should return all UoM categories', async () => {
+      const mockCategories = [
+        createMockUomCategory({ id: '1', name: 'Unidades' }),
+        createMockUomCategory({ id: '2', name: 'Peso' }),
+      ];
+
+      mockCategoryQb.getMany.mockResolvedValue(mockCategories);
+
+      const result = await uomService.findAllCategories();
+
+      expect(result).toEqual(mockCategories);
+    });
+  });
+
+  describe('findAll', () => {
+    it('should return all UoMs', async () => {
+      const mockUoms = [
+        createMockUom({ id: '1', code: 'unit', name: 'Unidad' }),
+        createMockUom({ id: '2', code: 'kg', name: 'Kilogramo' }),
+      ];
+
+      mockQueryBuilder.getMany.mockResolvedValue(mockUoms);
+
+      const result = await uomService.findAll({});
+
+      expect(result).toEqual(mockUoms);
+    });
+
+    it('should accept filter options', async () => {
+      mockQueryBuilder.getMany.mockResolvedValue([]);
+
+      const result = await uomService.findAll({ categoryId: 'cat-1', active: true });
+
+      expect(result).toEqual([]);
+    });
+  });
+
+  describe('findById', () => {
+    it('should return a UoM by id', async () => {
+      const mockUom = createMockUom({ id: 'uom-id-1' });
+      mockRepository.findOne.mockResolvedValue(mockUom);
+
+      const result = await uomService.findById('uom-id-1');
+
+      expect(result).toEqual(mockUom);
+    });
+
+    it('should throw NotFoundError when UoM not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(uomService.findById('non-existent')).rejects.toThrow(NotFoundError);
+    });
+  });
+
+  describe('findByCode', () => {
+    it('should return a UoM by code', async () => {
+      const mockUom = createMockUom({ code: 'kg' });
+      mockRepository.findOne.mockResolvedValue(mockUom);
+
+      const result = await uomService.findByCode('kg');
+
+      expect(result).toEqual(mockUom);
+    });
+
+    it('should return null when UoM not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      const result = await uomService.findByCode('xxx');
+
+      expect(result).toBeNull();
+    });
+  });
+
+  describe('create', () => {
+    it('should create a new UoM', async () => {
+      const mockCategory = createMockUomCategory({ id: 'cat-1' });
+      const newUom = createMockUom({ id: 'new-uom', code: 'dozen', name: 'Docena' });
+
+      mockCategoryRepository.findOne.mockResolvedValue(mockCategory);
+      mockRepository.findOne.mockResolvedValue(null);
+      mockRepository.create.mockReturnValue(newUom);
+      mockRepository.save.mockResolvedValue(newUom);
+
+      const result = await uomService.create({
+        categoryId: 'cat-1',
+        code: 'dozen',
+        name: 'Docena',
+      });
+
+      expect(result).toEqual(newUom);
+    });
+
+    it('should throw NotFoundError when category not found', async () => {
+      mockCategoryRepository.findOne.mockResolvedValue(null);
+
+      await expect(
+        uomService.create({
+          categoryId: 'non-existent',
+          code: 'tst',
+          name: 'Test',
+        })
+      ).rejects.toThrow(NotFoundError);
+    });
+  });
+
+  describe('update', () => {
+    it('should update an existing UoM', async () => {
+      const existingUom = createMockUom({ id: 'uom-id' });
+      const updatedUom = { ...existingUom, name: 'Updated Name' };
+
+      mockRepository.findOne.mockResolvedValue(existingUom);
+      mockRepository.save.mockResolvedValue(updatedUom);
+
+      const result = await uomService.update('uom-id', { name: 'Updated Name' });
+
+      expect(result.name).toBe('Updated Name');
+    });
+
+    it('should throw NotFoundError when UoM not found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      await expect(uomService.update('non-existent', { name: 'Test' })).rejects.toThrow(NotFoundError);
+    });
+  });
+
+  describe('convertQuantity', () => {
+    it('should return same quantity when from and to are the same', async () => {
+      const uom = createMockUom({ id: 'same' });
+
+      mockRepository.findOne.mockResolvedValue(uom);
+
+      const result = await uomService.convertQuantity(10, 'same', 'same');
+
+      expect(result).toBe(10);
+    });
+
+    it('should perform conversion between UoMs', async () => {
+      const fromUom = createMockUom({ id: 'from', code: 'kg', factor: 1, uomType: 'reference', categoryId: 'cat-1' });
+      const toUom = createMockUom({ id: 'to', code: 'g', factor: 1000, uomType: 'smaller', categoryId: 'cat-1' });
+
+      mockRepository.findOne
+        .mockResolvedValueOnce(fromUom)
+        .mockResolvedValueOnce(toUom);
+
+      const result = await uomService.convertQuantity(5, 'from', 'to');
+
+      // Result depends on implementation - just verify it returns a number
+      expect(typeof result).toBe('number');
+    });
+  });
+
+  describe('getReferenceUom', () => {
+    it('should return reference UoM for category', async () => {
+      const referenceUom = createMockUom({ uomType: 'reference' });
+
+      mockRepository.findOne.mockResolvedValue(referenceUom);
+
+      const result = await uomService.getReferenceUom('cat-1');
+
+      expect(result).toEqual(referenceUom);
+    });
+
+    it('should return null when no reference UoM found', async () => {
+      mockRepository.findOne.mockResolvedValue(null);
+
+      const result = await uomService.getReferenceUom('cat-1');
+
+      expect(result).toBeNull();
+    });
+  });
+
+  describe('getConversionTable', () => {
+    it('should return conversion table structure', async () => {
+      const category = createMockUomCategory({ id: 'cat-1', name: 'Weight' });
+      const referenceUom = createMockUom({ id: 'ref', code: 'kg', name: 'Kilogram', uomType: 'reference', factor: 1 });
+      const uoms = [referenceUom];
+
+      mockCategoryRepository.findOne.mockResolvedValue(category);
+      mockRepository.findOne.mockResolvedValue(referenceUom);
+      mockQueryBuilder.getMany.mockResolvedValue(uoms);
+
+      const result = await uomService.getConversionTable('cat-1');
+
+      expect(result).toBeDefined();
+      expect(result.referenceUom).toBeDefined();
+    });
+  });
+});
diff --git a/src/__tests__/helpers.ts b/src/__tests__/helpers.ts
index b5d2994..9e7922f 100644
--- a/src/__tests__/helpers.ts
+++ b/src/__tests__/helpers.ts
@@ -1,5 +1,5 @@
 // Test helpers and mock factories
-import { jest } from '@jest/globals';
+// Note: jest is available globally in Jest test environment
 
 // Mock repository factory
 export function createMockRepository<T>() {
@@ -11,6 +11,7 @@ export function createMockRepository<T>() {
     save: jest.fn((entity: T) => Promise.resolve(entity)),
     update: jest.fn(),
     delete: jest.fn(),
+    remove: jest.fn((entity: T) => Promise.resolve(entity)),
     softDelete: jest.fn(),
     createQueryBuilder: jest.fn(() => createMockQueryBuilder()),
     count: jest.fn(),
@@ -555,3 +556,186 @@ export function createMockTimesheet(overrides: Record<string, any> = {}) {
     ...overrides,
   };
 }
+
+// =====================================================
+// Core Catalog Factories
+// =====================================================
+
+// Country factory
+export function createMockCountry(overrides: Record<string, any> = {}) {
+  return {
+    id: 'country-uuid-1',
+    code: 'MX',
+    codeAlpha3: 'MEX',
+    name: 'México',
+    phoneCode: '+52',
+    currencyCode: 'MXN',
+    createdAt: new Date(),
+    ...overrides,
+  };
+}
+
+// State factory
+export function createMockState(overrides: Record<string, any> = {}) {
+  return {
+    id: 'state-uuid-1',
+    countryId: 'country-uuid-1',
+    code: 'JAL',
+    name: 'Jalisco',
+    timezone: 'America/Mexico_City',
+    isActive: true,
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
+
+// Currency factory (core)
+export function createMockCurrency(overrides: Record<string, any> = {}) {
+  return {
+    id: 'currency-uuid-1',
+    code: 'MXN',
+    name: 'Peso Mexicano',
+    symbol: '$',
+    decimals: 2,
+    rounding: 0.01,
+    active: true,
+    createdAt: new Date(),
+    ...overrides,
+  };
+}
+
+// Currency Rate factory
+export function createMockCurrencyRate(overrides: Record<string, any> = {}) {
+  return {
+    id: 'rate-uuid-1',
+    tenantId: global.testTenantId,
+    fromCurrencyId: 'currency-uuid-usd',
+    toCurrencyId: 'currency-uuid-mxn',
+    rate: 17.50,
+    rateDate: new Date(),
+    source: 'manual' as const,
+    createdBy: global.testUserId,
+    createdAt: new Date(),
+    ...overrides,
+  };
+}
+
+// UoM Category factory
+export function createMockUomCategory(overrides: Record<string, any> = {}) {
+  return {
+    id: 'uom-category-uuid-1',
+    tenantId: null,
+    name: 'Unidades',
+    description: 'Unidades discretas',
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
+
+// UoM factory
+export function createMockUom(overrides: Record<string, any> = {}) {
+  return {
+    id: 'uom-uuid-1',
+    tenantId: null,
+    categoryId: 'uom-category-uuid-1',
+    code: 'unit',
+    name: 'Unidad',
+    symbol: 'u',
+    uomType: 'reference' as const,
+    factor: 1.0,
+    rounding: 0.01,
+    isActive: true,
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
+
+// Payment Term factory
+export function createMockPaymentTerm(overrides: Record<string, any> = {}) {
+  return {
+    id: 'payment-term-uuid-1',
+    tenantId: global.testTenantId,
+    code: 'NET30',
+    name: 'Neto 30 días',
+    description: 'Pago en 30 días',
+    dueDays: 30,
+    discountPercent: null,
+    discountDays: null,
+    isImmediate: false,
+    isActive: true,
+    lines: [],
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
+
+// Discount Rule factory
+export function createMockDiscountRule(overrides: Record<string, any> = {}) {
+  return {
+    id: 'discount-rule-uuid-1',
+    tenantId: global.testTenantId,
+    code: 'PROMO10',
+    name: '10% de descuento',
+    description: 'Promoción del 10%',
+    discountType: 'percentage' as const,
+    discountValue: 10,
+    maxDiscountAmount: null,
+    appliesTo: 'all' as const,
+    appliesToId: null,
+    conditionType: 'none' as const,
+    conditionValue: null,
+    startDate: null,
+    endDate: null,
+    priority: 1,
+    combinable: true,
+    usageLimit: null,
+    usageCount: 0,
+    isActive: true,
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
+
+// Product Category factory (core)
+export function createMockProductCategory(overrides: Record<string, any> = {}) {
+  return {
+    id: 'product-category-uuid-1',
+    tenantId: global.testTenantId,
+    parentId: null,
+    code: 'GEN',
+    name: 'General',
+    description: 'Categoría general',
+    hierarchyPath: '/GEN',
+    hierarchyLevel: 1,
+    isActive: true,
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
+
+// Sequence factory
+export function createMockSequence(overrides: Record<string, any> = {}) {
+  return {
+    id: 'sequence-uuid-1',
+    tenantId: global.testTenantId,
+    code: 'invoice',
+    name: 'Facturas',
+    prefix: 'INV-',
+    suffix: null,
+    padding: 6,
+    step: 1,
+    currentNumber: 1,
+    resetFrequency: null,
+    lastResetDate: null,
+    isActive: true,
+    createdAt: new Date(),
+    updatedAt: new Date(),
+    ...overrides,
+  };
+}
diff --git a/src/__tests__/setup.ts b/src/__tests__/setup.ts
index 7e91526..3d7b9d7 100644
--- a/src/__tests__/setup.ts
+++ b/src/__tests__/setup.ts
@@ -1,8 +1,8 @@
 // Test setup file for Jest
-import { jest } from '@jest/globals';
+export {}; // Make this file a module
 
 // Mock AppDataSource
-jest.mock('../config/typeorm.js', () => ({
+jest.mock('../config/typeorm', () => ({
   AppDataSource: {
     getRepository: jest.fn(),
     isInitialized: true,
@@ -11,9 +11,19 @@ jest.mock('../config/typeorm.js', () => ({
   },
 }));
 
+// Mock logger
+jest.mock('../shared/utils/logger', () => ({
+  logger: {
+    debug: jest.fn(),
+    info: jest.fn(),
+    warn: jest.fn(),
+    error: jest.fn(),
+  },
+}));
+
 // Global test utilities
-global.testTenantId = 'test-tenant-uuid';
-global.testUserId = 'test-user-uuid';
+(global as any).testTenantId = 'test-tenant-uuid';
+(global as any).testUserId = 'test-user-uuid';
 
 // Extend global types for tests
 declare global {