tests: refactors redirection tests to avoid race condition - #14342

Pull request overview

This PR refactors two redirect-related unit tests to use a shared loopback redirect server helper, aiming to eliminate test flakiness/race conditions seen when multiple tests create/tear down their own listeners.

Changes:

• Replaced per-test HttpListener-based redirect setups with a shared RedirectLoopbackServer helper.
• Updated redirect tests to use the helper’s BaseUri and to assert redirect-target access via a shared flag.
• Added a new TCP-based loopback server utility under the unit test support folder.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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MAF Automated Review — Iteration 1

Result: No findings
Scope: full PR (2 commit(s)): 2c018ec638d2, f8847407170a
Model: claude-opus-4.8

Overview

This test-only change replaces two flaky redirect tests — each of which spun up an HttpListener on a Random-guessed port with a fire-and-forget Task.Run loop — with a shared internal RedirectLoopbackServer helper bound to an ephemeral loopback port and torn down deterministically via IAsyncDisposable/await using. The redesign removes the actual race (colliding guessed ports across parallel test classes) and makes teardown deterministic by awaiting the server task. Correctness of the "redirect is not followed" assertion is anchored by the plugins' non-redirecting HttpClient (AllowAutoRedirect=false), so exactly one well-formed GET /start reaches the helper and /secret is never contacted. The project builds cleanly on the declared net10.0 target, and all TFM-gated socket/reader overloads resolve. The two residual robustness gaps in the helper (a Split(' ')[1] crash / false-positive contacted-flag, and unguarded HandleRequestAsync faults surfacing through DisposeAsync) are real but confined to abnormal loopback conditions and are already tracked verbatim by the two unresolved reviewer threads, so no new publishable finding remains.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
No publishable findings remained after source verification for this scope.

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

        var requestTarget = requestLine?.Split(' ')[1];
        if (requestTarget == "/start")
        {
            var response = $"HTTP/1.1 302 Found\r\nLocation: {new Uri(this.BaseUri, this._redirectTargetPath.TrimStart('/'))}\r\nContent-Length: 0\r\nConnection: close\r\n\r\n";
            await stream.WriteAsync(Encoding.ASCII.GetBytes(response), cancellationToken).ConfigureAwait(false);