starting mdc pattern test
empty mdc, no key specified in pattern : 
empty mdc, key1 in pattern : 
empty mdc, key2 in pattern : 
empty mdc, key3 in pattern : 
empty mdc, key1, key2, and key3 in pattern : ,,
filled mdc, no key specified in pattern : 
filled mdc, key1 in pattern : value1
filled mdc, key2 in pattern : value2
filled mdc, key3 in pattern : 
filled mdc, key1, key2, and key3 in pattern : value1,value2,
finished mdc pattern test