@Test
    public void testParseNullValue() throws GuacamoleException {
        assertNull(FAVORITE_FISH.parseValue(null));
    }
Verifies that the absence of a property value (null) is parsed by
EnumGuacamoleProperty as the absence of an enum constant (also null).

@throws GuacamoleException
    If a valid test value is incorrectly recognized by parseValue() as
    invalid.
guacamole-ext/src/test/java/org/apache/guacamole/properties/EnumGuacamolePropertyTest.java