There has to be some form of limit on the output that's displayed in a cell of the result table. Too much output would flood the browser and and waste space in the database (since all output is recorded there for every run). Simply truncating the output can lose you important output at the end of the run, such as an exception being thrown. So I chose to snip the middle out of the output and mark it as '<...snip...>'. I also limit line lengths and the number of lines.
If you really want to do your own thing you can write a combinator template grader, which can generate whatever output it likes, although there is fundamentally a limit on the amount of output a run can generate, enforced by Jobe.
I suggest trying to find a way to pose a question in such a way that a correct solution doesn't generate screeds of output. What is the learning outcome of the question you're asking the student? Does it really need megabytes of output to verify that the learning outcome has been achieved?