structures and methods are disclosed for parallel biasing and testing , at dc and high frequency , of two or more read heads within a two dimensional magnetic recording slider . testing of heads comprises both conventional tests of the individual heads within the slider , as well as tests for interactions between the heads which are very closely spaced within the slider and thus may exhibit various magnetic , capacitive , ohmic , and stress - related interactions not seen in non - tdmr heads having only a single read head . overall testing times are nearly the same as for single head testing .