diff --git a/tests/iam/__init__.py b/tests/iam/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/iam/test_auth.py b/tests/iam/test_auth.py
new file mode 100644
index 00000000..54117b53
--- /dev/null
+++ b/tests/iam/test_auth.py
@@ -0,0 +1,43 @@
+from ydb.iam.auth import BaseJWTCredentials
+from unittest.mock import patch, mock_open
+
+CONTENT1 = '{"service_account_id":"my_sa", "id":"123", "private_key":"pppp", "user_account_id":"ua_id"}'
+CONTENT2 = '{"id":"123", "private_key":"pppp", "user_account_id":"ua_id"}'
+
+
+class FakeAuth(BaseJWTCredentials):
+    def __init__(self, account_id, key_id, private_key, iam_endpoint=None, iam_channel_credentials=None):
+        self.account_id = account_id
+        self.key_id = key_id
+        self.private_key = private_key
+        self.iam_endpoint = iam_endpoint
+        self.iam_channel_credentials = iam_channel_credentials
+
+    def __eq__(self, other):
+        return self.__dict__ == other.__dict__ if type(self) == type(other) else False
+
+
+@patch("builtins.open", new_callable=mock_open, read_data=CONTENT1)
+def test_auth_from_file(mock_file):
+    r1 = FakeAuth.from_file("my_file.json", iam_endpoint="my_iam_address", iam_channel_credentials="my_creds")
+    mock_file.assert_called_with("my_file.json", "r")
+
+    r2 = FakeAuth.from_content(CONTENT1, iam_endpoint="my_iam_address", iam_channel_credentials="my_creds")
+    assert r1 == r2
+    assert r1.__dict__ == {
+        "account_id": "my_sa",
+        "key_id": "123",
+        "private_key": "pppp",
+        "iam_endpoint": "my_iam_address",
+        "iam_channel_credentials": "my_creds",
+    }
+
+    r3 = FakeAuth.from_content(CONTENT2)
+
+    assert r3.__dict__ == {
+        "account_id": "ua_id",
+        "key_id": "123",
+        "private_key": "pppp",
+        "iam_endpoint": None,
+        "iam_channel_credentials": None,
+    }
diff --git a/ydb/iam/auth.py b/ydb/iam/auth.py
index 613b92ad..51345240 100644
--- a/ydb/iam/auth.py
+++ b/ydb/iam/auth.py
@@ -101,9 +101,7 @@ def from_file(cls, key_file, iam_endpoint=None, iam_channel_credentials=None):
         with open(os.path.expanduser(key_file), "r") as r:
             key = r.read()
 
-        return BaseJWTCredentials.from_content(
-            cls, key, iam_endpoint=iam_endpoint, iam_channel_credentials=iam_channel_credentials
-        )
+        return cls.from_content(key, iam_endpoint=iam_endpoint, iam_channel_credentials=iam_channel_credentials)
 
     @classmethod
     def from_content(cls, key, iam_endpoint=None, iam_channel_credentials=None):