Initialize lockdown cache singleton once per test function

[Copilot]

Closes: #issue

Description

Tests calling stubRepoAccessCache() created separate singleton instances due to sync.Once semantics—first initialization won, subsequent calls with different mock clients were ignored. This caused test failures when subtests needed specific GraphQL mock behavior.

Changes

pkg/lockdown/lockdown.go

• Added ResetInstance() to clear singleton state between tests

Test files (pkg/github/issues_test.go, pkg/github/pullrequests_test.go, pkg/lockdown/lockdown_test.go)

• Initialize cache once at test function start via ResetInstance() + GetInstance()
• Subtests conditionally reset when requiring custom mock clients
• 11 test functions updated across 3 files

Example

func Test_GetIssue(t *testing.T) {
    // Initialize once for all subtests
    gqlClient := githubv4.NewClient(nil)
    lockdown.ResetInstance()
    lockdown.GetInstance(gqlClient, lockdown.WithTTL(5*time.Minute))
    
    // Subtests share the same cache instance
    for _, tc := range tests {
        t.Run(tc.name, func(t *testing.T) {
            if tc.gqlHTTPClient != nil {
                // Reset only when custom mock needed
                lockdown.ResetInstance()
                gqlClient = githubv4.NewClient(tc.gqlHTTPClient)
            }
            // ...
        })
    }
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/graphql
  • Triggering command: /tmp/go-build1162513046/b001/github.test -test.testlogfile=/tmp/go-build1162513046/b001/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true -test.run=Test_GetIssue (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Update all tests using lockdown cache and make them initialize cache only once instead of separately for each test.

The user has attached the following file paths as relevant context:

• .github/copilot-instructions.md

Created from VS Code via the GitHub Pull Request extension.

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[stasyu2009-ux]

Код потрібно вставити готовий
і все

[stasyu2009-ux]

func Test_GetIssue(t testing.T) {
// Initialize once for all subtests
gqlClient := githubv4.NewClient(nil)
lockdown.ResetInstance()
lockdown.GetInstance(gqlClient, lockdown.WithTTL(5time.Minute))

// Subtests share the same cache instance
for _, tc := range tests {
    t.Run(tc.name, func(t *testing.T) {
        if tc.gqlHTTPClient != nil {
            // Reset only when custom mock needed
            lockdown.ResetInstance()
            gqlClient = githubv4.NewClient(tc.gqlHTTPClient)
        }
        // ...
    })
}

}