test(mcp): fix flaky OAuth tests by not sharing http.DefaultTransport#3704
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httptest.Server.Close calls http.DefaultTransport.CloseIdleConnections, which broke in-flight requests of parallel tests sharing the default transport (seen in CI as "transport connection broken: http: CloseIdleConnections called" in TestOAuthTransport_NonInteractiveCtxSkipsElicitation). Each test now uses a private transport via a newTestTransport helper. Assisted-By: Claude (Anthropic)
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Jul 17, 2026
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Assessment: 🟢 APPROVE
The fix is sound. newTestTransport correctly allocates a fresh *http.Transport{} per test, and t.Cleanup(tr.CloseIdleConnections) ensures draining happens even on test failure. All 15 http.DefaultTransport substitutions and the one http.DefaultClient.Do replacement are correctly wired. No bugs, races, or resource leaks were introduced by the changed lines.
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CI on main was intermittently failing with
TestOAuthTransport_NonInteractiveCtxSkipsElicitationreporting "net/http: HTTP/1.x transport connection broken: http: CloseIdleConnections called". The failure appeared on a commit that only touched workflow YAML, which made it hard to track down. The root cause was that all ~15 parallel tests inpkg/tools/mcp/oauth_test.gosharedhttp.DefaultTransportas the base transport for their OAuth wrappers. The Go stdlib'shttptest.Server.Closecallshttp.DefaultTransport.CloseIdleConnections, so whenever any test tore down its server it could kill an in-flight connection belonging to another test running concurrently.The fix adds a
newTestTransport(t *testing.T)helper that allocates a fresh*http.Transportper test and registers at.Cleanupto close its idle connections. All 15base: http.DefaultTransportsites and the onehttp.DefaultClient.Docall in the test file are replaced with per-test transports. No production code is touched.The OAuth tests were stress-tested with
-race -count=20 -parallel=16across the fullpkg/tools/mcppackage with no failures.