[Test]: Several edge cases are missing from copilot-rule.test.ts

[flanny7]

Hello, I always appreciate rulesync.

Problem

While copilot-rule.test.ts is fairly comprehensive at 1,133 lines, I found several edge cases that are not covered and could hide existing bugs.

Missing Test Cases

1. Complex comma-separated glob patterns in applyTo

The current test for applyTo splitting covers a simple single-pattern case. The following patterns are untested:

• Multiple patterns: "src/**/*.ts,tests/**/*.test.ts"
• Patterns with surrounding whitespace: "*.ts , *.js" (trimming)
• Duplicate patterns: "*.ts,*.ts"
• Special characters: "src/{components,utils}/**/*.ts"

2. excludeAgent: "code-review" roundtrip

Only excludeAgent: "coding-agent" is tested in roundtrip scenarios. The "code-review" value lacks equivalent coverage.

3. applyTo being undefined or empty string

The behavior when applyTo is absent or empty is not explicitly tested. Expected: globs should be undefined.

4. Global mode + non-root path combination

getSettablePaths({ global: true }) is tested for the root file, but the non-root path (.copilot/instructions/) is not verified.

5. YAML serialization of special characters in description

The description field is not tested with values containing quotes, newlines, or Markdown syntax (# Heading), which can affect YAML serialization behavior.

Reference

Similar patterns are tested in cursor-rule.test.ts (e.g., complex globs at line 391, empty globs at line 232–249), which may serve as a reference for what to add here.

Your consideration would be appreciated.