@Override
    public T setAll(Headers<? extends K, ? extends V, ?> headers) {
        throw new UnsupportedOperationException("read only");
    }
@Test
    public void testSetAll() {
        assertThrows(UnsupportedOperationException.class, new Executable() {
            @Override
            public void execute() {
                HEADERS.setAll(new TestEmptyHeaders());
            }
        });
    }