diff --git a/test/integration/test_sagemaker_extension_wrapper.py b/test/integration/test_sagemaker_extension_wrapper.py
index 059e377..9088f1c 100644
--- a/test/integration/test_sagemaker_extension_wrapper.py
+++ b/test/integration/test_sagemaker_extension_wrapper.py
@@ -7,7 +7,8 @@
     activate_languages,
     assert_connection_exists,
     assert_run_empty_udf,
-    get_script_counts
+    get_script_counts,
+    set_language_definition,
 )
 
 
@@ -22,10 +23,14 @@ def test_initialize_sme_extension(
     secrets.save(CKey.aws_access_key_id, "FAKEKEYIDDONTUSEIT")
     secrets.save(CKey.aws_secret_access_key, "FakeSecretAccessKeyDontTryToUseIt")
 
-    # Run the extension deployment.
-    initialize_sme_extension(secrets)
-
     with open_pyexasol_connection(secrets) as pyexasol_connection:
+        # Set pre-existing language definition with the chosen alias.
+        language_alias = 'PYTHON3_SME'
+        set_language_definition(language_alias, pyexasol_connection)
+
+        # Run the extension deployment.
+        initialize_sme_extension(secrets, language_alias=language_alias)
+
         activate_languages(pyexasol_connection, secrets)
         assert_run_empty_udf("PYTHON3_SME", pyexasol_connection, secrets)
         script_counts = get_script_counts(pyexasol_connection, secrets)
diff --git a/test/integration/test_transformers_extension_wrapper.py b/test/integration/test_transformers_extension_wrapper.py
index 4f60cf8..991669a 100644
--- a/test/integration/test_transformers_extension_wrapper.py
+++ b/test/integration/test_transformers_extension_wrapper.py
@@ -10,7 +10,8 @@
     activate_languages,
     assert_connection_exists,
     assert_run_empty_udf,
-    get_script_counts
+    get_script_counts,
+    set_language_definition,
 )
 
 
@@ -26,6 +27,9 @@ def test_initialize_te_extension(
 
     with open_pyexasol_connection(secrets) as pyexasol_connection:
 
+        # Set pre-existing language definition with the chosen alias.
+        set_language_definition(language_alias, pyexasol_connection)
+
         # Run the extension deployment.
         initialize_te_extension(secrets, language_alias=language_alias)
 
diff --git a/test/unit/test_extension_wrapper_common.py b/test/unit/test_extension_wrapper_common.py
index 9080589..343477e 100644
--- a/test/unit/test_extension_wrapper_common.py
+++ b/test/unit/test_extension_wrapper_common.py
@@ -9,10 +9,12 @@
 from exasol.nb_connector.ai_lab_config import AILabConfig as CKey
 from exasol.nb_connector.extension_wrapper_common import encapsulate_bucketfs_credentials
 
+DB_HOST = '1.2.3.4'
+
 
 @pytest.fixture
 def filled_secrets(secrets) -> Secrets:
-    secrets.save(CKey.db_host_name, 'localhost')
+    secrets.save(CKey.db_host_name, DB_HOST)
     secrets.save(CKey.db_port, '8888')
     secrets.save(CKey.db_user, 'user')
     secrets.save(CKey.db_password, 'password')
@@ -61,7 +63,7 @@ def test_bucketfs_credentials_default(mock_connect, filled_secrets):
     query_params = mock_connection.execute.call_args_list[0].kwargs['query_params']
     validate_params(query_params['BUCKETFS_ADDRESS'], (
         ['backend', 'url', 'service_name', 'bucket_name', 'path'],
-        ['onprem', 'https://localhost:6666', 'bfsdefault', 'default', path_in_bucket]
+        ['onprem', f'https://{DB_HOST}:6666', 'bfsdefault', 'default', path_in_bucket]
     ))
     validate_params(query_params['BUCKETFS_USER'], (
         ['username'], ['user']
@@ -71,6 +73,29 @@ def test_bucketfs_credentials_default(mock_connect, filled_secrets):
     ))
 
 
+def test_bucketfs_credentials_internal(mock_connect, filled_secrets):
+
+    path_in_bucket = 'location'
+    internal_host = 'localhost'
+    internal_port = 3377
+    filled_secrets.save(CKey.bfs_internal_host_name, internal_host)
+    filled_secrets.save(CKey.bfs_internal_port, str(internal_port))
+
+    mock_connection = unittest.mock.MagicMock()
+    mock_connection.__enter__.return_value = mock_connection
+    mock_connect.return_value = mock_connection
+
+    encapsulate_bucketfs_credentials(filled_secrets, path_in_bucket=path_in_bucket,
+                                     connection_name='whatever')
+
+    mock_connection.execute.assert_called_once()
+    query_params = mock_connection.execute.call_args_list[0].kwargs['query_params']
+    validate_params(query_params['BUCKETFS_ADDRESS'], (
+        ['backend', 'url', 'service_name', 'bucket_name', 'path'],
+        ['onprem', f'https://{internal_host}:{internal_port}', 'bfsdefault', 'default', path_in_bucket]
+    ))
+
+
 @unittest.mock.patch("pyexasol.connect")
 def test_bucketfs_credentials_verify(mock_connect, filled_secrets):
 
diff --git a/test/utils/integration_test_utils.py b/test/utils/integration_test_utils.py
index 2a31673..92be5a0 100644
--- a/test/utils/integration_test_utils.py
+++ b/test/utils/integration_test_utils.py
@@ -99,3 +99,12 @@ def assert_connection_exists(
         """
     ).fetchall()
     assert result
+
+
+def set_language_definition(language_alias: str, pyexasol_connection: ExaConnection
+                            ) -> None:
+    for alter_type in ['SYSTEM', 'SESSION']:
+        sql = (f"ALTER {alter_type} SET SCRIPT_LANGUAGES='PYTHON=builtin_python "
+               "R=builtin_r JAVA=builtin_java PYTHON3=builtin_python3 "
+               f"{language_alias}=builtin_python3';")
+        pyexasol_connection.execute(sql)