Add comprehensive tests for private/file-group.rkt

[Copilot]

The private/file-group.rkt module had only one test covering expand-modified-line-set, leaving most code paths untested.

Added Tests (24 new, 25 total)

• Struct constructors and predicates: file-portion, single-file-group, directory-file-group, package-file-group, git-repository-file-group
• File resolution:
  • Single file groups with range sets
  • Directory groups with .rkt filtering (non-.rkt files excluded)
  • Package groups using installed packages (e.g., rackunit)
  • Git repository groups with uncommitted changes detection
• Group aggregation: file-groups-resolve combining multiple groups and merging ranges for duplicate files
• Helper functions: rkt-file? extension filtering, range-bound-map for bounded/unbounded ranges

Tests use temporary directories/files in /tmp and clean up after themselves. Git tests configure user identity locally and verify command success.

(test-case "file-group-resolve returns only .rkt files"
  (define test-dir (make-temporary-file "resyntax-test-~a" 'directory))
  (define rkt-file1 (build-path test-dir "test1.rkt"))
  (define txt-file (build-path test-dir "test.txt"))
  ;; Only test1.rkt and test2.rkt are returned, test.txt is filtered out
  (define portions (file-group-resolve (directory-file-group test-dir)))
  (check-equal? (length portions) 2))

Original prompt

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This section details on the original issue you should resolve

<issue_title>File group code has poor coverage</issue_title>
<issue_description>The private/file-group.rkt file has very poor test coverage. This should be fixable with some tests that create directories, files, and git repositories in a /tmp directory.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes File group code has poor coverage #651

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[coveralls]

Pull Request Test Coverage Report for Build #63

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 93.744%

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Totals
Change from base Build #62:	0.4%
Covered Lines:	14476
Relevant Lines:	15442

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💛 - Coveralls