Add tests.

tests/unit/test_client.py

@@ -14,10 +14,12 @@
 import time
 import urllib
 import uuid
-from typing import Dict, Optional
+from contextlib import nullcontext as does_not_raise
+from typing import Any, Dict, Optional
 from unittest import mock
 from urllib.parse import urlparse
 
+import gssapi
 import httpretty
 import pytest
 import requests
@@ -865,6 +867,73 @@ def test_extra_credential_value_encoding(mock_get_and_post):
     assert headers[constants.HEADER_EXTRA_CREDENTIAL] == "foo=bar+%E7%9A%84"
 
 
+class MockGssapiCredentials:
+    def __init__(self, name: gssapi.Name, usage: str):
+        self.name = name
+        self.usage = usage
+
+    def __eq__(self, other: Any) -> bool:
+        if not isinstance(other, MockGssapiCredentials):
+            return False
+        return (
+            self.name == other.name,
+            self.usage == other.usage,
+        )
+
+
+@pytest.fixture
+def mock_gssapi_creds(monkeypatch):
+    monkeypatch.setattr("gssapi.Credentials", MockGssapiCredentials)
+
+
+def _gssapi_uname(spn: str):
+    return gssapi.Name(spn, gssapi.NameType.user)
+
+
+def _gssapi_sname(principal: str):
+    return gssapi.Name(principal, gssapi.NameType.hostbased_service)
+
+
+@pytest.mark.parametrize(
+    "options, expected_credentials, expected_hostname, expected_exception",
+    [
+        (
+            {}, None, None, does_not_raise(),
+        ),
+        (
+            {"hostname_override": "foo"}, None, "foo", does_not_raise(),
+        ),
+        (
+            {"service_name": "bar"}, None, None,
+            pytest.raises(ValueError, match=r"must be used together with hostname_override"),
+        ),
+        (
+            {"hostname_override": "foo", "service_name": "bar"}, None, _gssapi_sname("bar@foo"), does_not_raise(),
+        ),
+        (
+            {"principal": "foo"}, MockGssapiCredentials(_gssapi_uname("foo"), "initial"), None, does_not_raise(),
+        ),
+    ]
+)
+def test_authentication_gssapi_init_arguments(
+    options,
+    expected_credentials,
+    expected_hostname,
+    expected_exception,
+    mock_gssapi_creds,
+    monkeypatch,
+):
+    auth = GSSAPIAuthentication(**options)
+
+    session = requests.Session()
+
+    with expected_exception:
+        auth.set_http_session(session)
+
+        assert session.auth.target_name == expected_hostname
+        assert session.auth.creds == expected_credentials
+
+
 class RetryRecorder(object):
     def __init__(self, error=None, result=None):
         self.__name__ = "RetryRecorder"