[test-improver] Improve tests for proxy package

[github-actions]

Test Improvements: forward_to_github_test.go

File Analyzed

• Test File: internal/proxy/forward_to_github_test.go
• Package: internal/proxy
• Lines Added: +63

Improvements Made

1. Increased Coverage

• ✅ Added TestUpstreamHost table-driven test covering all three parsing branches of Server.upstreamHost()
• Previous Coverage: upstreamHost 37.5% (3/8 statements)
• New Coverage: upstreamHost 100% (8/8 statements)
• Package Improvement: 90.8% → 91.5% total

2. Better Testing Patterns

• ✅ Table-driven test with 7 cases covering distinct code paths
• ✅ Descriptive case names explaining why each case exercises a specific branch
• ✅ Inline comments documenting which parsing strategy each case exercises

3. Coverage of All Three Parsing Strategies

The upstreamHost function uses three strategies in order:

1. Full URL with scheme (https://api.github.com) — url.Parse returns non-empty Host directly
2. Scheme-less hostname (api.github.com, api.github.com/api/v3) — first parse gives empty Host (treated as relative path), so the function prepends https:// and re-parses
3. Unresolvable fallback (empty string) — both parse attempts yield empty Host, falls back to strings.Cut

Previously only the first strategy was exercised (by indirect coverage through forwardToGitHub tests using a httptest.Server URL).

Test Execution

All tests pass:

=== RUN   TestUpstreamHost
--- PASS: TestUpstreamHost (0.00s)
    --- PASS: TestUpstreamHost/full_URL_with_scheme_returns_hostname
    --- PASS: TestUpstreamHost/full_URL_with_port_strips_port_from_hostname
    --- PASS: TestUpstreamHost/http_URL_with_port_strips_port_from_hostname
    --- PASS: TestUpstreamHost/scheme-less_hostname_uses_second-parse_path
    --- PASS: TestUpstreamHost/scheme-less_hostname_with_path_strips_path
    --- PASS: TestUpstreamHost/leading_slashes_are_stripped_before_second_parse
    --- PASS: TestUpstreamHost/empty_URL_returns_empty_string_via_fallback
ok  github.com/github/gh-aw-mcpg/internal/proxy  0.075s  coverage: 91.5%

Why These Changes?

upstreamHost had 37.5% coverage despite being used in production code to populate the server.address OpenTelemetry attribute. The scheme-less and fallback paths — designed to handle common deployment configurations like api.github.com or GHES without an explicit https:// prefix — were completely untested. The new tests verify all three parsing strategies and document the intended behaviour for each URL format.

---

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Generated by Test Improver · sonnet46 3.5M · ◷

[Copilot]

Pull request overview

This PR improves test coverage and clarity for Server.upstreamHost() in the internal/proxy package, ensuring all parsing branches are exercised and the expected hostname extraction behavior is documented through table-driven cases.

Changes:

• Added a new table-driven TestUpstreamHost covering scheme URLs, scheme-less hostnames (with/without paths), and empty input fallback behavior.
• Expanded branch coverage for upstreamHost() without introducing network dependencies or non-deterministic test behavior.

Show a summary per file

File	Description
internal/proxy/forward_to_github_test.go	Adds comprehensive table-driven coverage for Server.upstreamHost() hostname extraction branches.

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