FessActionAdjustmentProvider provider = new FessActionAdjustmentProvider(fessConfig);
        final Map<String, String> headerMap = new HashMap<>();
        provider.adjustActionResponseHeaders("text/plain", (k, v) -> headerMap.put(k, v));

        assertEquals(0, headerMap.size());
    }

    @Test
    public void test_write_defaultHeadersOnly() throws Exception {