[test-improver] Improve tests for cmd/flags_difc

[github-actions]

File Analyzed

• Test File: internal/cmd/flags_difc_test.go
• Package: internal/cmd

Improvements Made

1. Better Testing Patterns

• ✅ Replaced manual os.Setenv/defer/os.Unsetenv with t.Setenv in TestGetDefaultDIFCMode — cleaner, race-safe, and automatic cleanup

2. Increased Coverage

• ✅ Added test for consecutive commas ("safeoutputs,,github") — covers the previously untested continue branch that skips empty parts after splitting
• ✅ Added test for trailing comma ("safeoutputs,github,") — covers the same empty-part skip path from a different angle
• ✅ Added test for tab character in server IDs — verifies whitespace detection beyond just space (the ContainsAny check covers " \t\n\r")
• Previous Coverage (parseDIFCSinkServerIDs): 93.3%
• New Coverage (parseDIFCSinkServerIDs): 100.0%

3. Cleaner & More Stable Tests

• ✅ t.Setenv automatically restores env vars after each subtest, eliminating the manual save/restore pattern and making tests safer under parallelism

Test Execution

All cmd package tests pass:

ok  	github.com/github/gh-aw-mcpg/internal/cmd	0.125s	coverage: 46.7% of statements

(TestFetchAndFixSchema_NetworkError in the config package is a pre-existing failure unrelated to these changes.)

Why These Changes?

parseDIFCSinkServerIDs had a dead continue branch (for empty segments produced by consecutive or trailing commas) that was never exercised. Adding those test cases brings the function to 100% coverage and documents the expected parsing behavior. Switching to t.Setenv removes boilerplate and prevents tests from accidentally leaking environment state.

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Focuses on better patterns, increased coverage, and more stable tests

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[Copilot]

Pull request overview

Improves the stability and branch coverage of DIFC-related CLI flag tests in internal/cmd, primarily by simplifying environment variable handling and adding missing edge-case parsing scenarios.

Changes:

• Replaced manual env var save/restore logic with t.Setenv in TestGetDefaultDIFCMode.
• Added coverage for empty-segment cases in parseDIFCSinkServerIDs (consecutive/trailing commas).
• Added a test case to verify tab whitespace is rejected in server IDs.

Show a summary per file

File	Description
internal/cmd/flags_difc_test.go	Uses t.Setenv for cleaner env-var tests and adds cases to fully exercise sink server ID parsing edge cases.

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• Files reviewed: 1/1 changed files
• Comments generated: 0