public void start(ProxyService service) {
        extensions.values().forEach(extension -> extension.start(service));
    }
@Test
    public void testStart() {
        ProxyService service = mock(ProxyService.class);
        extensions.start(service);
        verify(extension1, times(1)).start(same(service));
        verify(extension2, times(1)).start(same(service));
    }