added new unittests

[Hendrik-code]

increase code coverage by adding lots of new unittests

[Copilot]

Pull request overview

This PR expands unit test coverage across several TPTBox core modules (vertebra constants, NumPy utilities, and NII I/O / morphology) and cleans up some boilerplate (sys.path hacks, duplicate imports) in existing test files. It also adds a pytest.ini_options section to silence deprecation/future warnings and refines the coverage exclude patterns.

Changes:

• Add new test classes covering Vertebra_Instance region accessors, navigation helpers, Location enum, and vert_subreg_labels.
• Add new test classes covering many np_utils functions (bbox, point coords, translate-to-center, convex hull, Betti numbers, majority label overlap, top-k indices) and NII I/O + morphology (erode_msk, dilate_msk, fill_holes, get_seg_array, from_numpy, save/load round-trip).
• Remove sys.path manipulation and redundant imports from existing test files; configure pytest warning filters and tighten coverage exclude regex patterns in pyproject.toml.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
unit_tests/test_vertconstants.py	Drops sys.path boilerplate; adds tests for region accessors, navigation helpers, and Location enum.
unit_tests/test_nputils.py	Removes sys.path/noqa boilerplate from import block.
unit_tests/test_nputils_extended.py	Adds tests for bbox, point coords, translate-to-center, convex hull, Betti numbers, majority label overlap, top-k.
unit_tests/test_nii.py	Removes unused sys/Path imports and a duplicate nibabel import inside a method.
unit_tests/test_nii_io.py	New file: save/load round-trip and from_numpy factory tests.
unit_tests/test_nii_extended.py	Adds tests for erode_msk/dilate_msk, fill_holes, and get_seg_array.
pyproject.toml	Adds pytest warning filters; refines coverage exclude patterns.

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