Test/add more test

[rajibola]

Description

This PR adds several test cases to enhance the robustness and correctness of our regex-related functionality. The new tests ensure that key features behave as expected and handle edge cases appropriately. Specifically, the following scenarios are now covered:

• startCaptureGroup: Verifies that capturing groups are created correctly.
• nonWordBoundary: Ensures that non-word boundary assertions work as intended.
• unicodeChar with variant 'l': Confirms that Unicode characters with the 'l' variant match accurately.
• Error Handling:
  • Throws an error when an invalid Unicode letter variant is provided.
  • Throws an error if there is no pattern available to repeat.

These additions improve test coverage, reduce the risk of regressions, and provide better validation for edge cases in regex processing.

Notes

• If additional edge cases are identified, further tests can be added in future iterations.
• This PR does not introduce any changes to the production code; it focuses solely on improving test coverage.