diff --git a/promo_code/business/tests/__init__.py b/promo_code/business/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/promo_code/business/tests/auth/__init__.py b/promo_code/business/tests/auth/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/promo_code/business/tests/auth/base.py b/promo_code/business/tests/auth/base.py
new file mode 100644
index 0000000..3f32203
--- /dev/null
+++ b/promo_code/business/tests/auth/base.py
@@ -0,0 +1,23 @@
+import business.models
+import django.urls
+import rest_framework
+import rest_framework.status
+import rest_framework.test
+
+
+class BaseBusinessAuthTestCase(rest_framework.test.APITestCase):
+    @classmethod
+    def setUpTestData(cls):
+        super().setUpTestData()
+        cls.client = rest_framework.test.APIClient()
+        cls.signup_url = django.urls.reverse('api-business:company-sign-up')
+        cls.signin_url = django.urls.reverse('api-business:company-sign-in')
+        cls.protected_url = django.urls.reverse('api-core:protected')
+        cls.valid_data = {
+            'name': 'Digital Marketing Solutions Inc.',
+            'email': 'testcompany@example.com',
+            'password': 'SecurePass123!',
+        }
+
+    def tearDown(self):
+        business.models.Company.objects.all().delete()
diff --git a/promo_code/business/tests/auth/test_authentication.py b/promo_code/business/tests/auth/test_authentication.py
new file mode 100644
index 0000000..46d43ae
--- /dev/null
+++ b/promo_code/business/tests/auth/test_authentication.py
@@ -0,0 +1,33 @@
+import business.models
+import business.tests.auth.base
+import rest_framework.status
+import rest_framework.test
+
+
+class AuthenticationTests(business.tests.auth.base.BaseBusinessAuthTestCase):
+    def test_signin_success(self):
+        registration_data = {**self.valid_data, 'email': 'unique@company.com'}
+        business.models.Company.objects.create_company(
+            name=registration_data['name'],
+            email=registration_data['email'],
+            password=registration_data['password'],
+        )
+        self.assertTrue(
+            business.models.Company.objects.filter(
+                email=registration_data['email'],
+            ).exists(),
+        )
+
+        response = self.client.post(
+            self.signin_url,
+            {
+                'email': registration_data['email'],
+                'password': registration_data['password'],
+            },
+            format='json',
+        )
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
+        self.assertIn('access', response.data)
diff --git a/promo_code/business/tests/auth/test_registration.py b/promo_code/business/tests/auth/test_registration.py
new file mode 100644
index 0000000..44e87c1
--- /dev/null
+++ b/promo_code/business/tests/auth/test_registration.py
@@ -0,0 +1,25 @@
+import business.models
+import business.tests.auth.base
+import rest_framework.status
+import rest_framework.test
+
+
+class TestCompanyRegistration(
+    business.tests.auth.base.BaseBusinessAuthTestCase,
+):
+    def test_registration_success(self):
+        registration_data = {**self.valid_data, 'email': 'unique@company.com'}
+        response = self.client.post(
+            self.signup_url,
+            registration_data,
+            format='json',
+        )
+        self.assertTrue(
+            business.models.Company.objects.filter(
+                email=registration_data['email'],
+            ).exists(),
+        )
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
diff --git a/promo_code/business/tests/auth/test_tokens.py b/promo_code/business/tests/auth/test_tokens.py
new file mode 100644
index 0000000..b2ab66a
--- /dev/null
+++ b/promo_code/business/tests/auth/test_tokens.py
@@ -0,0 +1,84 @@
+import business.models
+import business.tests.auth.base
+import rest_framework.status
+import rest_framework.test
+
+
+class JWTTests(business.tests.auth.base.BaseBusinessAuthTestCase):
+    def setUp(self):
+        super().setUp()
+        business.models.Company.objects.create_company(
+            name='Digital Marketing Solutions Inc.',
+            email='testcompany@example.com',
+            password='SuperStrongPassword2000!',
+        )
+
+        self.user_data = {
+            'email': 'testcompany@example.com',
+            'password': 'SuperStrongPassword2000!',
+        }
+
+    def test_access_protected_view_with_valid_token(self):
+        response = self.client.post(
+            self.signin_url,
+            self.user_data,
+            format='json',
+        )
+
+        token = response.data['access']
+
+        self.client.credentials(HTTP_AUTHORIZATION='Bearer ' + token)
+        response = self.client.get(self.protected_url)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
+        self.assertEqual(response.data['status'], 'request was permitted')
+
+    def test_registration_token_invalid_after_login(self):
+        data = {
+            'email': 'test@example.com',
+            'password': 'StrongPass123!cd',
+            'name': 'Digital Marketing Solutions Inc.',
+        }
+        response = self.client.post(
+            self.signup_url,
+            data,
+            format='json',
+        )
+        reg_access_token = response.data['access']
+
+        self.client.credentials(
+            HTTP_AUTHORIZATION=f'Bearer {reg_access_token}',
+        )
+        response = self.client.get(self.protected_url)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
+
+        login_data = {'email': data['email'], 'password': data['password']}
+        response = self.client.post(
+            self.signin_url,
+            login_data,
+            format='json',
+        )
+        login_access_token = response.data['access']
+
+        self.client.credentials(
+            HTTP_AUTHORIZATION=f'Bearer {reg_access_token}',
+        )
+        response = self.client.get(self.protected_url)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_401_UNAUTHORIZED,
+        )
+
+        self.client.credentials(
+            HTTP_AUTHORIZATION=f'Bearer {login_access_token}',
+        )
+        response = self.client.get(self.protected_url)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
diff --git a/promo_code/business/tests/auth/test_validation.py b/promo_code/business/tests/auth/test_validation.py
new file mode 100644
index 0000000..e8a37af
--- /dev/null
+++ b/promo_code/business/tests/auth/test_validation.py
@@ -0,0 +1,118 @@
+import business.models
+import business.tests.auth.base
+import parameterized
+import rest_framework.status
+import rest_framework.test
+
+
+class InvalidCompanyRegistrationTestCase(
+    business.tests.auth.base.BaseBusinessAuthTestCase,
+):
+    def test_duplicate_email_registration(self):
+        business.models.Company.objects.create_company(
+            name=self.valid_data['name'],
+            email=self.valid_data['email'],
+            password=self.valid_data['password'],
+        )
+        self.assertTrue(
+            business.models.Company.objects.filter(
+                email=self.valid_data['email'],
+            ).exists(),
+        )
+
+        response = self.client.post(
+            self.signup_url,
+            self.valid_data,
+            format='json',
+        )
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_409_CONFLICT,
+        )
+
+    @parameterized.parameterized.expand(
+        [
+            ('short_password_1', 'easypwd'),
+            ('short_password_2', 'Ar1@!$'),
+            ('no_digits', 'PasswordWithoutDigits'),
+            ('no_special_chars', 'PasswordWithoutSpecial1'),
+            ('common_phrase', 'whereismymoney777'),
+            ('missing_uppercase', 'lowercase123$'),
+            ('missing_lowercase', 'UPPERCASE123$'),
+            ('non_ascii', 'Päss123$!AAd'),
+            ('emoji', '😎werY!!*Dj3sd'),
+        ],
+    )
+    def test_invalid_password_cases(self, _, invalid_password):
+        test_data = {**self.valid_data, 'password': invalid_password}
+        response = self.client.post(self.signup_url, test_data, format='json')
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_400_BAD_REQUEST,
+            f'Failed for password: {invalid_password}',
+        )
+
+    @parameterized.parameterized.expand(
+        [
+            ('domain_missing_dot', 'a@b'),
+            ('domain_missing_dot', 'test@dom'),
+            ('missing_local_part', '@domain.com'),
+            ('missing_at_symbol', 'missing.at.sign'),
+            ('multiple_at_symbols', 'double@@at.com'),
+        ],
+    )
+    def test_invalid_email_cases(self, _, invalid_email):
+        test_data = {**self.valid_data, 'email': invalid_email}
+        response = self.client.post(self.signup_url, test_data, format='json')
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_400_BAD_REQUEST,
+            f'Failed for email: {invalid_email}',
+        )
+
+    def test_short_company_name(self):
+        test_data = {**self.valid_data, 'name': 'A'}
+        response = self.client.post(self.signup_url, test_data, format='json')
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_400_BAD_REQUEST,
+        )
+
+
+class InvalidCompanyAuthenticationTestCase(
+    business.tests.auth.base.BaseBusinessAuthTestCase,
+):
+    @parameterized.parameterized.expand(
+        [
+            ('missing_password', {'email': 'valid@example.com'}, 'password'),
+            ('missing_email', {'password': 'any'}, 'email'),
+            ('empty_data', {}, ['email', 'password']),
+        ],
+    )
+    def test_missing_required_fields(self, case_name, data, expected_fields):
+        response = self.client.post(self.signin_url, data, format='json')
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_400_BAD_REQUEST,
+        )
+
+    def test_signin_invalid_password(self):
+        business.models.Company.objects.create_company(
+            email=self.valid_data['email'],
+            name=self.valid_data['name'],
+            password=self.valid_data['password'],
+        )
+
+        data = {
+            'email': self.valid_data['email'],
+            'password': 'SuperInvalidPassword2000!',
+        }
+        response = self.client.post(
+            self.signin_url,
+            data,
+            format='json',
+        )
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_401_UNAUTHORIZED,
+        )
diff --git a/promo_code/user/tests/auth/base.py b/promo_code/user/tests/auth/base.py
index d8d58f8..fc13f54 100644
--- a/promo_code/user/tests/auth/base.py
+++ b/promo_code/user/tests/auth/base.py
@@ -5,7 +5,7 @@
 import user.models
 
 
-class BaseAuthTestCase(rest_framework.test.APITestCase):
+class BaseUserAuthTestCase(rest_framework.test.APITestCase):
     @classmethod
     def setUpTestData(cls):
         super().setUpTestData()
diff --git a/promo_code/user/tests/auth/test_authentication.py b/promo_code/user/tests/auth/test_authentication.py
index 5e71bca..e545ff7 100644
--- a/promo_code/user/tests/auth/test_authentication.py
+++ b/promo_code/user/tests/auth/test_authentication.py
@@ -5,7 +5,7 @@
 import user.tests.auth.base
 
 
-class AuthenticationTests(user.tests.auth.base.BaseAuthTestCase):
+class UserAuthenticationTests(user.tests.auth.base.BaseUserAuthTestCase):
     def test_signin_success(self):
         user.models.User.objects.create_user(
             email='minecraft.digger@gmail.com',
diff --git a/promo_code/user/tests/auth/test_registration.py b/promo_code/user/tests/auth/test_registration.py
index 07783c9..1759ce2 100644
--- a/promo_code/user/tests/auth/test_registration.py
+++ b/promo_code/user/tests/auth/test_registration.py
@@ -5,7 +5,7 @@
 import user.tests.auth.base
 
 
-class RegistrationTests(user.tests.auth.base.BaseAuthTestCase):
+class UserRegistrationTests(user.tests.auth.base.BaseUserAuthTestCase):
     def test_registration_success(self):
         valid_data = {
             'name': 'Emma',
diff --git a/promo_code/user/tests/auth/test_tokens.py b/promo_code/user/tests/auth/test_tokens.py
index c4031ea..d3fb812 100644
--- a/promo_code/user/tests/auth/test_tokens.py
+++ b/promo_code/user/tests/auth/test_tokens.py
@@ -6,7 +6,7 @@
 import user.tests.auth.base
 
 
-class JWTTests(user.tests.auth.base.BaseAuthTestCase):
+class JWTTests(user.tests.auth.base.BaseUserAuthTestCase):
     def setUp(self):
         super().setUp()
         user.models.User.objects.create_user(
@@ -33,7 +33,10 @@ def test_access_protected_view_with_valid_token(self):
 
         self.client.credentials(HTTP_AUTHORIZATION='Bearer ' + token)
         response = self.client.get(self.protected_url)
-        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
         self.assertEqual(response.data['status'], 'request was permitted')
 
     def test_registration_token_invalid_after_login(self):
@@ -55,7 +58,10 @@ def test_registration_token_invalid_after_login(self):
             HTTP_AUTHORIZATION=f'Bearer {reg_access_token}',
         )
         response = self.client.get(self.protected_url)
-        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
 
         login_data = {'email': data['email'], 'password': data['password']}
         response = self.client.post(
@@ -69,13 +75,19 @@ def test_registration_token_invalid_after_login(self):
             HTTP_AUTHORIZATION=f'Bearer {reg_access_token}',
         )
         response = self.client.get(self.protected_url)
-        self.assertEqual(response.status_code, 401)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_401_UNAUTHORIZED,
+        )
 
         self.client.credentials(
             HTTP_AUTHORIZATION=f'Bearer {login_access_token}',
         )
         response = self.client.get(self.protected_url)
-        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            response.status_code,
+            rest_framework.status.HTTP_200_OK,
+        )
 
     def test_refresh_token_invalidation_after_new_login(self):
         first_login_response = self.client.post(
diff --git a/promo_code/user/tests/auth/test_validation.py b/promo_code/user/tests/auth/test_validation.py
index a52f742..4f357ec 100644
--- a/promo_code/user/tests/auth/test_validation.py
+++ b/promo_code/user/tests/auth/test_validation.py
@@ -6,7 +6,9 @@
 import user.tests.auth.base
 
 
-class RegistrationTestCase(user.tests.auth.base.BaseAuthTestCase):
+class InvalidUserRegistrationTestCase(
+    user.tests.auth.base.BaseUserAuthTestCase,
+):
     def test_email_duplication(self):
         valid_data = {
             'name': 'Emma',
@@ -42,24 +44,6 @@ def test_email_duplication(self):
             rest_framework.status.HTTP_409_CONFLICT,
         )
 
-    def test_invalid_email_format(self):
-        data = {
-            'name': 'Emma',
-            'surname': 'Thompson',
-            'email': 'dota.fan',
-            'password': 'SuperStrongPassword2000!',
-            'other': {'age': 23, 'country': 'us'},
-        }
-        response = self.client.post(
-            self.signup_url,
-            data,
-            format='json',
-        )
-        self.assertEqual(
-            response.status_code,
-            rest_framework.status.HTTP_400_BAD_REQUEST,
-        )
-
     @parameterized.parameterized.expand(
         [
             ('common_phrase', 'whereismymoney777'),
@@ -292,7 +276,9 @@ def test_empty_surname_field(self):
         )
 
 
-class AuthenticationTestCase(user.tests.auth.base.BaseAuthTestCase):
+class InvalidUserAuthenticationTestCase(
+    user.tests.auth.base.BaseUserAuthTestCase,
+):
     @parameterized.parameterized.expand(
         [
             ('missing_password', {'email': 'valid@example.com'}, 'password'),