t.idleMu.Lock()
	defer t.idleMu.Unlock()
	for key := range t.idleConn {
		keys = append(keys, key.String())
	}
	slices.Sort(keys)
	return
}

func (t *Transport) IdleConnKeyCountForTesting() int {
	t.idleMu.Lock()
	defer t.idleMu.Unlock()
	return len(t.idleConn)
}

func (t *Transport) IdleConnStrsForTesting() []string {
	var ret []string
	t.idleMu.Lock()

	if err != nil {
		t.Fatal(err)
	}
	if string(slurp) != "ok" {
		t.Fatalf("got %q; want ok", slurp)
	}

	waitCondition(t, 1*time.Millisecond, func(d time.Duration) bool {
		if n := cst.tr.IdleConnKeyCountForTesting(); n != 0 {
			if d > 0 {
				t.Logf("%v idle conns still present after %v", n, d)
			}
			return false
		}
		return true
	})
	if got := logout.String(); got != "" {