if rb.Free() != 64 {
		t.Fatalf("expect free 64 bytes but got %d. r.w=%d, r.r=%d", rb.Free(), rb.w, rb.r)
	}
	if rb.r != 16 {
		t.Fatalf("expect r.r=16 but got %d. r.w=%d", rb.r, rb.w)
	}
}

func TestRingBuffer_Blocking(t *testing.T) {
	// Typical runtime is ~5-10s.
	defer timeout(60 * time.Second)()
	const debug = false

	var readBytes int
	var wroteBytes int
	var readBuf bytes.Buffer
	var wroteBuf bytes.Buffer