    @Test
    public void applySystemPropertiesShouldConvertOptsToSystemProps() {

        System.setProperty("c", "");
        Map<String, String> opts = new HashMap<>();
        opts.put("a", "1");
        opts.put("-Dc", "2");
        CoffeeHouseApp.applySystemProperties(opts);
        assertThat(System.getProperty("c")).isEqualTo("2");
    }