public abstract long observeWm(int queueIndex, long wmValue);
@Test
    public void when_i1_idle_i2_idle_then_noNewWmMessageForwardedImmediately() {
        assertEquals(Long.MIN_VALUE, wc.observeWm(0, IDLE_MESSAGE.timestamp()));
        assertEquals(NO_NEW_WM, wc.observeWm(1, IDLE_MESSAGE.timestamp()));
    }