    @Test
    public void putNewTraceHeaderValueInsideUnmodifiableList() {

        Map<String, Collection<String>> headers = new HashMap<>();
        headers.put("x-header", Collections.unmodifiableList(Arrays.asList("123:123:123:1")));
        HttpHeadersInjectAdapter adapter = new HttpHeadersInjectAdapter(headers);

        adapter.put("x-header", "123:456:456:1");

        assertEquals(headers.get("x-header"), Arrays.asList("123:123:123:1", "123:456:456:1"));
    }