[Neuralman159]

Summary
Adds unit tests to improve test coverage in humanize.number.

Changes

1. Added a test to verify that clamp() raises ValueError when an invalid format argument is provided;
2. Added parameterized tests for intcomma() to verify number formatting with alternative thousands and decimal separators;
3. Used pytest's monkeypatch fixture to test separator formatting independently of installed translations.

Test Coverage
Metric Before After
Overall coverage 98.75% 99.29%
Covered statements 554/561 557/561
Uncovered statements 7 4

Testing

1. Test framework: pytest;
2. Coverage tool: pytest-cov;
3. All newly added test cases passed;
4. No production code was modified.

[hugovk]

What's "Lab2"?

[hugovk]

Closing as duplicate of PR #492. See #512.