public String getMetricsName(Message in, String defaultValue) {
        return getStringHeader(in, MetricsConstants.HEADER_METRIC_NAME, defaultValue);
    }
@Test
    public void testGetMetricsName() {
        when(in.getHeader(HEADER_METRIC_NAME, String.class)).thenReturn("A");
        assertThat(okProducer.getMetricsName(in, "value"), is("A"));
        inOrder.verify(in, times(1)).getHeader(HEADER_METRIC_NAME, String.class);
        inOrder.verifyNoMoreInteractions();
    }