public Set<String> exposedHeaders() {
        return Collections.unmodifiableSet(exposeHeaders);
    }
@Test
    public void exposeHeaders() {
        final CorsConfig cors = forAnyOrigin().exposeHeaders("custom-header1", "custom-header2").build();
        assertThat(cors.exposedHeaders(), hasItems("custom-header1", "custom-header2"));
    }