openml · PGijsbers · Feb 19, 2026 · Jan 20, 2026 · Jan 21, 2026 · Jan 28, 2026
diff --git a/openml/cli.py b/openml/cli.py
@@ -109,7 +109,7 @@ def check_server(server: str) -> str:
 
  def replace_shorthand(server: str) -> str:
  if server == "test":
- return "https://test.openml.org/api/v1/xml"
+ return f"{config.TEST_SERVER_URL}/api/v1/xml"
  if server == "production_server":
  return "https://www.openml.org/api/v1/xml"
  return server

diff --git a/openml/config.py b/openml/config.py
@@ -28,6 +28,8 @@
 OPENML_TEST_SERVER_ADMIN_KEY_ENV_VAR = "OPENML_TEST_SERVER_ADMIN_KEY"
 _TEST_SERVER_NORMAL_USER_KEY = "normaluser"
 
+TEST_SERVER_URL = "https://test.openml.org"
+
 
 class _Config(TypedDict):
  apikey: str
@@ -214,7 +216,7 @@ class ConfigurationForExamples:
  _last_used_server = None
  _last_used_key = None
  _start_last_called = False
- _test_server = "https://test.openml.org/api/v1/xml"
+ _test_server = f"{TEST_SERVER_URL}/api/v1/xml"
  _test_apikey = _TEST_SERVER_NORMAL_USER_KEY
 
  @classmethod
@@ -470,7 +472,8 @@ def get_cache_directory() -> str:
 
  """
  url_suffix = urlparse(server).netloc
- reversed_url_suffix = os.sep.join(url_suffix.split(".")[::-1]) # noqa: PTH118
+ url_parts = url_suffix.replace(":", "_").split(".")[::-1]
+ reversed_url_suffix = os.sep.join(url_parts) # noqa: PTH118
  return os.path.join(_root_cache_directory, reversed_url_suffix) # noqa: PTH118
 
 

diff --git a/openml/tasks/functions.py b/openml/tasks/functions.py
@@ -415,9 +415,10 @@ def get_task(
  if not isinstance(task_id, int):
  raise TypeError(f"Task id should be integer, is {type(task_id)}")
 
- cache_key_dir = openml.utils._create_cache_directory_for_id(TASKS_CACHE_DIR_NAME, task_id)
- tid_cache_dir = cache_key_dir / str(task_id)
- tid_cache_dir_existed = tid_cache_dir.exists()
+ task_cache_directory = openml.utils._create_cache_directory_for_id(
+ TASKS_CACHE_DIR_NAME, task_id
+ )
+ task_cache_directory_existed = task_cache_directory.exists()
  try:
  task = _get_task_description(task_id)
  dataset = get_dataset(task.dataset_id, **get_dataset_kwargs)
@@ -431,8 +432,8 @@ def get_task(
  if download_splits and isinstance(task, OpenMLSupervisedTask):
  task.download_split()
  except Exception as e:
- if not tid_cache_dir_existed:
- openml.utils._remove_cache_dir_for_id(TASKS_CACHE_DIR_NAME, tid_cache_dir)
+ if not task_cache_directory_existed:
+ openml.utils._remove_cache_dir_for_id(TASKS_CACHE_DIR_NAME, task_cache_directory)
  raise e
 
  return task

diff --git a/openml/testing.py b/openml/testing.py
@@ -47,7 +47,7 @@ class TestBase(unittest.TestCase):
  "user": [],
  }
  flow_name_tracker: ClassVar[list[str]] = []
- test_server = "https://test.openml.org/api/v1/xml"
+ test_server = f"{openml.config.TEST_SERVER_URL}/api/v1/xml"
  admin_key = os.environ.get(openml.config.OPENML_TEST_SERVER_ADMIN_KEY_ENV_VAR)
  user_key = openml.config._TEST_SERVER_NORMAL_USER_KEY
 

diff --git a/tests/conftest.py b/tests/conftest.py
@@ -277,7 +277,7 @@ def with_server(request):
  openml.config.apikey = None
  yield
  return
- openml.config.server = "https://test.openml.org/api/v1/xml"
+ openml.config.server = f"{openml.config.TEST_SERVER_URL}/api/v1/xml"
  openml.config.apikey = TestBase.user_key
  yield
 

diff --git a/tests/files/localhost_8000 b/tests/files/localhost_8000
@@ -0,0 +1 @@
+org/openml/test
diff --git a/tests/test_datasets/test_dataset_functions.py b/tests/test_datasets/test_dataset_functions.py
@@ -527,27 +527,20 @@ def test_deletion_of_cache_dir(self):
  def test_deletion_of_cache_dir_faulty_download(self, patch):
  patch.side_effect = Exception("Boom!")
  self.assertRaisesRegex(Exception, "Boom!", openml.datasets.get_dataset, dataset_id=1)
- datasets_cache_dir = os.path.join(self.workdir, "org", "openml", "test", "datasets")
+ datasets_cache_dir = os.path.join(openml.config.get_cache_directory(), "datasets")
  assert len(os.listdir(datasets_cache_dir)) == 0
 
  @pytest.mark.test_server()
  def test_publish_dataset(self):
- # lazy loading not possible as we need the arff-file.
- openml.datasets.get_dataset(3, download_data=True)
- file_path = os.path.join(
- openml.config.get_cache_directory(),
- "datasets",
- "3",
- "dataset.arff",
- )
+ arff_file_path = self.static_cache_dir / "org" / "openml" / "test" / "datasets" / "2" / "dataset.arff"
  dataset = OpenMLDataset(
  "anneal",
  "test",
  data_format="arff",
  version=1,
  licence="public",
  default_target_attribute="class",
- data_file=file_path,
+ data_file=arff_file_path,
  )
  dataset.publish()
  TestBase._mark_entity_for_removal("data", dataset.dataset_id)
@@ -890,7 +883,7 @@ def test_create_invalid_dataset(self):
 
  @pytest.mark.test_server()
  def test_get_online_dataset_arff(self):
- dataset_id = 100 # Australian
+ dataset_id = 128 # iris -- one of the few datasets without parquet file
  # lazy loading not used as arff file is checked.
  dataset = openml.datasets.get_dataset(dataset_id, download_data=True)
  decoder = arff.ArffDecoder()
@@ -1468,8 +1461,9 @@ def test_data_edit_critical_field(self):
  raise e
  time.sleep(10)
  # Delete the cache dir to get the newer version of the dataset
+
  shutil.rmtree(
- os.path.join(self.workdir, "org", "openml", "test", "datasets", str(did)),
+ os.path.join(openml.config.get_cache_directory(), "datasets", str(did)),
  )
 
  @pytest.mark.test_server()
@@ -1734,7 +1728,6 @@ def test_delete_dataset(self):
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_dataset_not_owned(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = (
  test_files_directory / "mock_responses" / "datasets" / "data_delete_not_owned.xml"
  )
@@ -1749,14 +1742,13 @@ def test_delete_dataset_not_owned(mock_delete, test_files_directory, test_api_ke
  ):
  openml.datasets.delete_dataset(40_000)
 
- dataset_url = "https://test.openml.org/api/v1/xml/data/40000"
+ dataset_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/data/40000"
  assert dataset_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_dataset_with_run(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = (
  test_files_directory / "mock_responses" / "datasets" / "data_delete_has_tasks.xml"
  )
@@ -1771,14 +1763,13 @@ def test_delete_dataset_with_run(mock_delete, test_files_directory, test_api_key
  ):
  openml.datasets.delete_dataset(40_000)
 
- dataset_url = "https://test.openml.org/api/v1/xml/data/40000"
+ dataset_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/data/40000"
  assert dataset_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_dataset_success(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = (
  test_files_directory / "mock_responses" / "datasets" / "data_delete_successful.xml"
  )
@@ -1790,14 +1781,13 @@ def test_delete_dataset_success(mock_delete, test_files_directory, test_api_key)
  success = openml.datasets.delete_dataset(40000)
  assert success
 
- dataset_url = "https://test.openml.org/api/v1/xml/data/40000"
+ dataset_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/data/40000"
  assert dataset_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_unknown_dataset(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = (
  test_files_directory / "mock_responses" / "datasets" / "data_delete_not_exist.xml"
  )
@@ -1812,7 +1802,7 @@ def test_delete_unknown_dataset(mock_delete, test_files_directory, test_api_key)
  ):
  openml.datasets.delete_dataset(9_999_999)
 
- dataset_url = "https://test.openml.org/api/v1/xml/data/9999999"
+ dataset_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/data/9999999"
  assert dataset_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
@@ -1907,9 +1897,8 @@ def _dataset_features_is_downloaded(did: int):
 
 
 def _dataset_data_file_is_downloaded(did: int):
- parquet_present = _dataset_file_is_downloaded(did, "dataset.pq")
- arff_present = _dataset_file_is_downloaded(did, "dataset.arff")
- return parquet_present or arff_present
+ cache_directory = Path(openml.config.get_cache_directory()) / "datasets" / str(did)
+ return any(f.suffix in (".pq", ".arff") for f in cache_directory.iterdir())
 
 
 def _assert_datasets_retrieved_successfully(
@@ -2014,7 +2003,7 @@ def test_get_dataset_parquet(requests_mock, test_files_directory):
  test_files_directory / "mock_responses" / "datasets" / "data_description_61.xml"
  )
  # While the mocked example is from production, unit tests by default connect to the test server.
- requests_mock.get("https://test.openml.org/api/v1/xml/data/61", text=content_file.read_text())
+ requests_mock.get(f"{openml.config.TEST_SERVER_URL}/api/v1/xml/data/61", text=content_file.read_text())
  dataset = openml.datasets.get_dataset(61, download_data=True)
  assert dataset._parquet_url is not None
  assert dataset.parquet_file is not None

diff --git a/tests/test_flows/test_flow_functions.py b/tests/test_flows/test_flow_functions.py
@@ -453,7 +453,6 @@ def test_delete_flow(self):
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_flow_not_owned(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "flows" / "flow_delete_not_owned.xml"
  mock_delete.return_value = create_request_response(
  status_code=412,
@@ -466,14 +465,13 @@ def test_delete_flow_not_owned(mock_delete, test_files_directory, test_api_key):
  ):
  openml.flows.delete_flow(40_000)
 
- flow_url = "https://test.openml.org/api/v1/xml/flow/40000"
+ flow_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/flow/40000"
  assert flow_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_flow_with_run(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "flows" / "flow_delete_has_runs.xml"
  mock_delete.return_value = create_request_response(
  status_code=412,
@@ -486,14 +484,13 @@ def test_delete_flow_with_run(mock_delete, test_files_directory, test_api_key):
  ):
  openml.flows.delete_flow(40_000)
 
- flow_url = "https://test.openml.org/api/v1/xml/flow/40000"
+ flow_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/flow/40000"
  assert flow_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_subflow(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "flows" / "flow_delete_is_subflow.xml"
  mock_delete.return_value = create_request_response(
  status_code=412,
@@ -506,14 +503,13 @@ def test_delete_subflow(mock_delete, test_files_directory, test_api_key):
  ):
  openml.flows.delete_flow(40_000)
 
- flow_url = "https://test.openml.org/api/v1/xml/flow/40000"
+ flow_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/flow/40000"
  assert flow_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_flow_success(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "flows" / "flow_delete_successful.xml"
  mock_delete.return_value = create_request_response(
  status_code=200,
@@ -523,15 +519,14 @@ def test_delete_flow_success(mock_delete, test_files_directory, test_api_key):
  success = openml.flows.delete_flow(33364)
  assert success
 
- flow_url = "https://test.openml.org/api/v1/xml/flow/33364"
+ flow_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/flow/33364"
  assert flow_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 @pytest.mark.xfail(reason="failures_issue_1544", strict=False)
 def test_delete_unknown_flow(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "flows" / "flow_delete_not_exist.xml"
  mock_delete.return_value = create_request_response(
  status_code=412,
@@ -544,6 +539,6 @@ def test_delete_unknown_flow(mock_delete, test_files_directory, test_api_key):
  ):
  openml.flows.delete_flow(9_999_999)
 
- flow_url = "https://test.openml.org/api/v1/xml/flow/9999999"
+ flow_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/flow/9999999"
  assert flow_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
diff --git a/tests/test_openml/test_config.py b/tests/test_openml/test_config.py
@@ -78,7 +78,7 @@ def test_get_config_as_dict(self):
  config = openml.config.get_config_as_dict()
  _config = {}
  _config["apikey"] = TestBase.user_key
- _config["server"] = "https://test.openml.org/api/v1/xml"
+ _config["server"] = f"{openml.config.TEST_SERVER_URL}/api/v1/xml"
  _config["cachedir"] = self.workdir
  _config["avoid_duplicate_runs"] = False
  _config["connection_n_retries"] = 20

diff --git a/tests/test_runs/test_run_functions.py b/tests/test_runs/test_run_functions.py
@@ -1813,7 +1813,6 @@ def test_initialize_model_from_run_nonstrict(self):
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_run_not_owned(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "runs" / "run_delete_not_owned.xml"
  mock_delete.return_value = create_request_response(
  status_code=412,
@@ -1826,14 +1825,13 @@ def test_delete_run_not_owned(mock_delete, test_files_directory, test_api_key):
  ):
  openml.runs.delete_run(40_000)
 
- run_url = "https://test.openml.org/api/v1/xml/run/40000"
+ run_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/run/40000"
  assert run_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_run_success(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "runs" / "run_delete_successful.xml"
  mock_delete.return_value = create_request_response(
  status_code=200,
@@ -1843,14 +1841,13 @@ def test_delete_run_success(mock_delete, test_files_directory, test_api_key):
  success = openml.runs.delete_run(10591880)
  assert success
 
- run_url = "https://test.openml.org/api/v1/xml/run/10591880"
+ run_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/run/10591880"
  assert run_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
 
 @mock.patch.object(requests.Session, "delete")
 def test_delete_unknown_run(mock_delete, test_files_directory, test_api_key):
- openml.config.start_using_configuration_for_example()
  content_file = test_files_directory / "mock_responses" / "runs" / "run_delete_not_exist.xml"
  mock_delete.return_value = create_request_response(
  status_code=412,
@@ -1863,7 +1860,7 @@ def test_delete_unknown_run(mock_delete, test_files_directory, test_api_key):
  ):
  openml.runs.delete_run(9_999_999)
 
- run_url = "https://test.openml.org/api/v1/xml/run/9999999"
+ run_url = f"{openml.config.TEST_SERVER_URL}/api/v1/xml/run/9999999"
  assert run_url == mock_delete.call_args.args[0]
  assert test_api_key == mock_delete.call_args.kwargs.get("params", {}).get("api_key")
 
@@ -1873,6 +1870,10 @@ def test_delete_unknown_run(mock_delete, test_files_directory, test_api_key):
  Version(sklearn.__version__) < Version("0.21"),
  reason="couldn't perform local tests successfully w/o bloating RAM",
  )
+@unittest.skipIf(
+ Version(sklearn.__version__) >= Version("1.8"),
+ reason="predictions differ significantly",
+ )
 @mock.patch("openml_sklearn.SklearnExtension._prevent_optimize_n_jobs")
 @pytest.mark.test_server()
 def test__run_task_get_arffcontent_2(parallel_mock):
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		org/openml/test
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