@Test
public void extractIntegerHeader_whenNoHeaderPresent_shouldReturnNull() throws Exception {

    // no header added to response
    assertThat(HeaderUtils.extractIntegerHeader(response, AD_TIMEOUT)).isNull();
    response.addHeader(AD_TIMEOUT.getKey(), null);
    assertThat(HeaderUtils.extractIntegerHeader(response, AD_TIMEOUT)).isNull();
}