@Test
    public void testValueOfWithDefault() {
        DefaultClientConfigImpl clientConfig = new DefaultClientConfigImpl();

        CustomValueOf prop = clientConfig.getOrDefault(CUSTOM_KEY);
        Assert.assertEquals("default", prop.getValue());
    }
Test cases to verify the correctness of the Client Configuration settings

@author stonse
ribbon-core/src/test/java/com/netflix/client/config/ClientConfigTest.java