I've just read below that it's a scheme course, i did a few lessons on that too and the approach was similar to what you describe. If with "bug" you are referring to syntax errors (being scheme, missing or wrong parenthesis), yeah, without a compiler/syntax checker it will be a bit hard to spot them sometimes. For algorithm testing, it's not different than what you'll do using a compiler, only slower (considering that testing usually involves testing various input combinations). Will, in this case, be a better course with the use of a compiler? Hard to tell, my impression is just that using only paper will make you focus more on the code you are writing, but this could not work for everyone.