Refactor test_base.py to pytest style (#1351)

[EshaSharma28]

Summary

This PR refactors test/test_pipeline/test_base.py to use modern pytest functional styles instead of the legacy unittest.TestCase structure, addressing #1351.

Changes

• Replaced the class-based BaseTest(unittest.TestCase) structure with independent test functions:
  • test_get_hyperparameter_configuration_space_3choices()
  • test_init_params_handling()
  • test_include_exclude_validation()
• Converted all legacy self.assertEqual assertions to standard Python assert statements.
• Replaced self.assertRaises / self.assertRaisesRegex context managers with pytest.raises.
• Cleaned up imports, removing unittest.

Verification

Ran tests successfully with pytest:

PYTHONPATH=. python3 -m pytest test/test_pipeline/test_base.py