public List<PushConnection> getAll() {
        return new ArrayList<>(clientPushConnectionMap.values());
    }
@Test
    void testGetAll() {
        pushConnectionRegistry.put("clientId1", pushConnection);
        pushConnectionRegistry.put("clientId2", pushConnection);

        List<PushConnection> connections = pushConnectionRegistry.getAll();

        assertEquals(2, connections.size());
    }