code: def testGroupTests(self):
      tests = [
          (Test(name="x1", group="x"), False),
          (Test(name="x2", group="x"), False),
          (Test(name="y1", group="y"), False),
          (Test(name="ungrouped"), False),
          (Test(name="x3", group="x"), False),
      ]
  
      grouped = group_tests(tests)
      self.assertEqual(len(grouped), 3)  # Three groups
      self.assertEqual(len(grouped["x"]), 3)
      self.assertSequenceEqual(
          [t["name"] for t, _ in grouped["x"]], ["x1", "x2", "x3"]
      )
      self.assertEqual(len(grouped["y"]), 1)
  
imports: import os
  import sys
  import tempfile
  import unittest
  from typing import Dict, Callable
  from unittest.mock import patch
  import yaml
  from github import Repository
  from ray_release.buildkite.concurrency import get_test_resources_from_cluster_compute, get_concurrency_group
  from ray_release.buildkite.filter import filter_tests, group_tests
  from ray_release.buildkite.settings import split_ray_repo_str, get_default_settings, update_settings_from_environment, Frequency, update_settings_from_buildkite, Priority, get_test_attr_regex_filters
  from ray_release.buildkite.step import get_step, RELEASE_QUEUE_DEFAULT, RELEASE_QUEUE_CLIENT, DOCKER_PLUGIN_KEY
  from ray_release.test import Test
  from ray_release.exception import ReleaseTestConfigError
  from ray_release.wheels import DEFAULT_BRANCH
label_desc: Use image node_id 8 for calling the BuildkiteSettingsTest obj's underlying member method code with example usage: obj.testGroupTests() without return types