diff --git a/tests/conftest.py b/tests/conftest.py
index 152ad5b..7036a44 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -5,6 +5,7 @@
 from sinch import SinchClient
 from sinch import SinchClientAsync
 from sinch.core.models.http_response import HTTPResponse
+from sinch.core.models.http_request import HttpRequest
 from sinch.domains.authentication.models.authentication import OAuthToken
 from sinch.core.models.base_model import SinchBaseModel, SinchRequestBaseModel
 
@@ -215,6 +216,19 @@ def verification_request_signature_timestamp():
     return os.getenv("VERIFICATION_REQUEST_SIGNATURE_TIMESTAMP")
 
 
+@pytest.fixture
+def empty_http_request():
+    return HttpRequest(
+        headers={},
+        protocol=None,
+        http_method=None,
+        request_body=None,
+        query_params=None,
+        url=None,
+        auth=None
+    )
+
+
 @pytest.fixture
 def http_response():
     return HTTPResponse(
diff --git a/tests/integration/test_http_transport.py b/tests/integration/test_http_transport.py
new file mode 100644
index 0000000..de792f4
--- /dev/null
+++ b/tests/integration/test_http_transport.py
@@ -0,0 +1,36 @@
+from sinch.core.adapters.requests_http_transport import HTTPTransportRequests
+from sinch.domains.sms.endpoints.sms_endpoint import SMSEndpoint
+from sinch.core.enums import HTTPAuthentication
+
+
+def test_authenticate_method_with_service_plan_id_version_of_sms_api(
+    sinch_client_sync_with_service_plan_id,
+    empty_http_request
+):
+    sms_endpoint = SMSEndpoint(
+        sinch=sinch_client_sync_with_service_plan_id,
+        request_data=empty_http_request
+    )
+    http_transport = HTTPTransportRequests(sinch=sinch_client_sync_with_service_plan_id)
+    http_transport.authenticate(endpoint=sms_endpoint, request_data=empty_http_request)
+
+    assert empty_http_request.headers
+    assert "Bearer" in empty_http_request.headers["Authorization"]
+    assert empty_http_request.headers["Content-Type"] == "application/json"
+
+
+def test_authenticate_method_with_project_id_version_of_sms_api(
+    sinch_client_sync,
+    empty_http_request
+):
+    sms_endpoint = SMSEndpoint(
+        sinch=sinch_client_sync,
+        request_data=empty_http_request,
+    )
+    sms_endpoint.HTTP_AUTHENTICATION = HTTPAuthentication.OAUTH.value
+    http_transport = HTTPTransportRequests(sinch=sinch_client_sync)
+    http_transport.authenticate(endpoint=sms_endpoint, request_data=empty_http_request)
+
+    assert empty_http_request.headers
+    assert "Bearer" in empty_http_request.headers["Authorization"]
+    assert empty_http_request.headers["Content-Type"] == "application/json"
diff --git a/tests/integration/test_sms_endpoint_credendials_formatting.py b/tests/integration/test_sms_endpoint_credendials_formatting.py
new file mode 100644
index 0000000..70fd6e1
--- /dev/null
+++ b/tests/integration/test_sms_endpoint_credendials_formatting.py
@@ -0,0 +1,23 @@
+from sinch.domains.sms.endpoints.sms_endpoint import SMSEndpoint
+from sinch.core.enums import HTTPAuthentication
+
+
+def test_sms_endpoint_service_plan_id_credentials_processing(sinch_client_sync_with_service_plan_id, service_plan_id):
+    sms_endpoint = SMSEndpoint(
+        sinch=sinch_client_sync_with_service_plan_id,
+        request_data={}
+    )
+    assert sms_endpoint.project_or_service_id == service_plan_id
+    assert sms_endpoint.HTTP_AUTHENTICATION == HTTPAuthentication.SMS_TOKEN.value
+    assert (
+        sms_endpoint.sms_origin == sinch_client_sync_with_service_plan_id.configuration._sms_origin_with_service_plan_id
+    )
+
+
+def test_sms_endpoint_with_project_id_credentials_processing(sinch_client_sync, project_id):
+    sms_endpoint = SMSEndpoint(
+        sinch=sinch_client_sync,
+        request_data={}
+    )
+    assert sms_endpoint.project_or_service_id == project_id
+    assert sms_endpoint.sms_origin == sinch_client_sync.configuration.sms_origin