Use __file__-relative path for test_model_serving_auth fixtures

test_model_serving_auth.py hardcoded "tests/testdata/model-serving-
test-token" assuming cwd == SDK root. That works for the upstream
`make test` invocation but breaks when pytest is launched from any
other directory (e.g. a Bazel test sandbox).

Switch to `pathlib.Path(__file__).parent / "testdata" / ...` so the
tests resolve their fixtures regardless of cwd.

Author: hectorcast-db

tests/test_model_serving_auth.py

@@ -1,3 +1,4 @@
+import pathlib
 import threading
 import time
 
@@ -8,6 +9,12 @@
 
 from .conftest import raises
 
+# Test fixture files live next to this test, regardless of where pytest
+# was invoked from.
+_TESTDATA = pathlib.Path(__file__).parent / "testdata"
+_MODEL_SERVING_TEST_TOKEN = str(_TESTDATA / "model-serving-test-token")
+_MODEL_SERVING_TEST_TOKEN_V2 = str(_TESTDATA / "model-serving-test-token-v2")
+
 default_auth_base_error_message = (
     "default auth: cannot configure default credentials, "
     "please check https://docs.databricks.com/en/dev-tools/auth.html#databricks-client-unified-authentication "
@@ -24,31 +31,31 @@
                 ("DB_MODEL_SERVING_HOST_URL", "x"),
             ],
             ["DATABRICKS_MODEL_SERVING_HOST_URL"],
-            "tests/testdata/model-serving-test-token",
+            _MODEL_SERVING_TEST_TOKEN,
         ),
         (
             [
                 ("IS_IN_DATABRICKS_MODEL_SERVING_ENV", "true"),
                 ("DB_MODEL_SERVING_HOST_URL", "x"),
             ],
             ["DATABRICKS_MODEL_SERVING_HOST_URL"],
-            "tests/testdata/model-serving-test-token",
+            _MODEL_SERVING_TEST_TOKEN,
         ),
         (
             [
                 ("IS_IN_DB_MODEL_SERVING_ENV", "true"),
                 ("DATABRICKS_MODEL_SERVING_HOST_URL", "x"),
             ],
             ["DB_MODEL_SERVING_HOST_URL"],
-            "tests/testdata/model-serving-test-token",
+            _MODEL_SERVING_TEST_TOKEN,
         ),
         (
             [
                 ("IS_IN_DATABRICKS_MODEL_SERVING_ENV", "true"),
                 ("DATABRICKS_MODEL_SERVING_HOST_URL", "x"),
             ],
             ["DB_MODEL_SERVING_HOST_URL"],
-            "tests/testdata/model-serving-test-token",
+            _MODEL_SERVING_TEST_TOKEN,
         ),
     ],
 )
@@ -92,7 +99,7 @@ def test_model_serving_auth(env_values, del_env_values, oauth_file_name, monkeyp
         ),  # In Model Serving and Invalid File Name
         (
             [],
-            "tests/testdata/model-serving-test-token",
+            _MODEL_SERVING_TEST_TOKEN,
         ),  # Not in Model Serving and Valid File Name
     ],
 )
@@ -122,7 +129,7 @@ def test_model_serving_auth_refresh(monkeypatch, mocker):
     # patch mlflow to read the file from the test directory
     monkeypatch.setattr(
         "databricks.sdk.credentials_provider.ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH",
-        "tests/testdata/model-serving-test-token",
+        _MODEL_SERVING_TEST_TOKEN,
     )
     mocker.patch("databricks.sdk.config.Config._known_file_config_loader")
 
@@ -136,7 +143,7 @@ def test_model_serving_auth_refresh(monkeypatch, mocker):
     # Simulate refreshing the token by patching to to a new file
     monkeypatch.setattr(
         "databricks.sdk.credentials_provider.ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH",
-        "tests/testdata/model-serving-test-token-v2",
+        _MODEL_SERVING_TEST_TOKEN_V2,
     )
 
     monkeypatch.setattr(
@@ -172,7 +179,7 @@ def test_agent_user_credentials(monkeypatch, mocker):
     monkeypatch.setenv("DB_MODEL_SERVING_HOST_URL", "x")
     monkeypatch.setattr(
         "databricks.sdk.credentials_provider.ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH",
-        "tests/testdata/model-serving-test-token",
+        _MODEL_SERVING_TEST_TOKEN,
     )
 
     invokers_token_val = "databricks_invokers_token"