Improve test coverage by adding comprehensive tests for utility functions and helpers

[Copilot]

Coverage Improvement Plan for easystats/report

Based on the issue comments, the package coverage has improved from 72.25% to 86.10%, but there's still room to push it towards 90%+. I've analyzed the current state and implemented significant coverage improvements.

Plan to increase coverage:

• Analyze current test coverage and identify low-coverage files
• Review existing tests to understand current coverage patterns
• Examine specific functions in low-coverage files

Coverage improvements implemented:

• Add tests for uncovered branches in utils_grouped_df.R (was 13.56%)

  • Added comprehensive tests for .group_indices(), .groups_drop(), .calculate_groups(), and error handling
  • Tests now cover factor handling, edge cases, and missing column scenarios

• Improve coverage for format_model.R helper functions (was 46.15%)

  • Added tests for format_model.character() method with all model types
  • Enhanced tests for get_model_type_prefix() helper via format_model calls
  • Added edge case tests for different GLM families and link functions

• Add tests for uncovered report_table.R methods (was 54.24%)

  • Comprehensive tests for as.report_table() with summary and as_is parameters
  • Tests for c.report_table() concatenation method
  • Enhanced coverage for .report_table_footer() and .report_table_caption() helpers
  • Added edge case tests for different alternative hypothesis formats

• Enhance report_effectsize.R test coverage (was 68.97%)

  • New dedicated test file for report_effectsize helper functions
  • Complete tests for .text_effectsize() with all interpretation methods
  • Comprehensive tests for .text_standardize() with all standardization methods
  • Tests for as.report_effectsize() and print.report_effectsize()

• Add enhanced coverage for report_s.R function (was 93.33%)

  • Added comprehensive edge case tests for parameter validation
  • Tests for p-value to s-value conversion and vice versa
  • Enhanced error handling validation for invalid inputs
  • Custom test parameter scenarios

• Resolve merge conflicts with main branch

Test suite status:

• All 620 tests pass with no failures
• No regressions introduced

Fixes #559.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[strengejacke]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved the merge conflict in DESCRIPTION (version field: kept 0.6.3.1 from main) and completed the merge in commit 9759a742. All 620 tests pass with no failures.