test: improve coverage for unit/unit.mbt

[rami3l]

Disclaimer: This PR was generated by an LLM agent as part of an experiment.

Summary

coverage of `unit/unit.mbt`: 66.7% -> 100%

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

Looking at the git diff, I'll analyze the added test cases for potential issues:

1. In the "Unit hash_combine test", there's a potential issue with the assertion. The test creates hasher2 but doesn't perform any hash_combine operation on it before comparing. This means it's comparing a hasher with combined unit value against an empty hasher, which might not be the intended test case.

2. The inspect! macro in the last test uses a string literal content="()", but many testing frameworks expect content comparisons without quotes. This might need to be content=() depending on the testing framework being used.

3. The test descriptions use inconsistent naming conventions - some use quoted strings ("Unit hash_combine test") while others don't (the original test above). This isn't a bug but could lead to maintenance issues and should be standardized.

These are observations based on common patterns and best practices. The severity of these issues depends on your specific testing framework and requirements.

[coveralls]

Pull Request Test Coverage Report for Build 5028

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 85.04%

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Totals
Change from base Build 5019:	0.03%
Covered Lines:	5224
Relevant Lines:	6143

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💛 - Coveralls