static Properties getSystemProperties() {
        String[] inputConfigSources = System.getProperty("proxyconfigsources",
                                                         DEFAULT_PROXY_CONFIG_SOURCES).split(",");
        return new Properties(inputConfigSources);
    }
@Test
    void testReadingSystemProperties() {
        ProxyServer.Properties properties = ProxyServer.getSystemProperties();
        assertEquals(1, properties.configSources.length);
        assertEquals(ProxyServer.DEFAULT_PROXY_CONFIG_SOURCES, properties.configSources[0]);
    }