[test] Add tests for envutil.deriveAPIFromServerURL — http scheme and edge cases

[github-actions]

Test Coverage Improvement: deriveAPIFromServerURL

Function Analyzed

• Package: internal/envutil
• Function: deriveAPIFromServerURL (in github.go)
• File: internal/envutil/github.go (line 83)
• Complexity: Medium (URL parsing, 3-way switch on hostname pattern, port extraction)

Why This Function?

deriveAPIFromServerURL contains several branches not exercised by the existing TestDeriveAPIFromServerURL (which only used https:// URLs):

1. `(redacted) scheme — explicitly supported (the guard at lines 91-94 allows both), but no test covered the GHEC or GHES code paths with plain HTTP.
2. Empty URL — url.Parse("") succeeds but leaves Host empty, triggering the parsed.Host == "" early-return guard. This path was not covered.
3. Trailing slash — strings.TrimRight(serverURL, "/") strips trailing slashes before parsing. This normalisation was not verified.

Tests Added

New file: internal/envutil/github_coverage_test.go

• ✅ (redacted) scheme with GHEC .ghe.comhostname →copilot-api.` subdomain
• ✅ `(redacted) scheme with GHEC + explicit port
• ✅ (redacted) scheme with GHES custom hostname → /api/v3` path
• ✅ `(redacted) scheme with GHES + explicit port
• ✅ Empty URL → "" (empty-host guard)
• ✅ github.com with trailing slash → same result as without (TrimRight branch)
• ✅ GHES URL with multiple trailing slashes (all stripped by TrimRight)

Coverage Report

Note: The network firewall in the CI/sandbox environment blocks proxy.golang.org, preventing go test execution. The tests are analytically verified: each case traces deriveAPIFromServerURL deterministically (pure URL parsing and string operations — no I/O, no randomness, no external dependencies).

Correctness Reasoning

Each new test case was traced manually through the function:

Input	Expected output	Path exercised
`(mycompany.ghe.com/redacted)	`(copilotapi.mycompany.ghe.com/redacted)	http scheme; .ghe.com → copilot-api, no port
`(mycompany.ghe.com/redacted)	`(copilotapi.mycompany.ghe.com/redacted)	Same with port branch
`(github.example.com/redacted)	`(github.example.com/redacted)	http scheme; GHES default
`(github.example.com/redacted)	`(github.example.com/redacted)	GHES with port
""	""	url.Parse("") → Host="" → early-return
https://github.com/	DefaultGitHubAPIBaseURL	TrimRight strips /
`(github.example.com/redacted)	`(github.example.com/redacted)	Multiple slashes stripped

---

Generated by Test Coverage Improver

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

• proxy.golang.org

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "proxy.golang.org"

See Network Configuration for more information.

Generated by Test Coverage Improver · sonnet46 17.2M · ◷

[Copilot]

Pull request overview

This PR improves unit coverage for internal/envutil URL derivation behavior without changing production code.

Changes:

• Adds table-driven tests for http:// GHEC and GHES server URL derivation.
• Adds edge-case coverage for empty input and trailing slash normalization.
• Verifies existing constants and helper behavior through direct tests of deriveAPIFromServerURL.

Show a summary per file

File	Description
internal/envutil/github_coverage_test.go	Adds focused coverage for deriveAPIFromServerURL scheme handling and edge cases.

Copilot's findings

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