i would recommend the test run...especially with this project, as there is no pattern per se`, just a list of measurements. the problem i kept running into was cutting one fabric the 0-3mth size and the other 3-6mth size. sounds stupid, i know, but because they're listed one after the other, it actually is quite easy to mix them up...and that was after reading and re-reading the directions before cutting.
the other thing you have to remember with Amy Butler is that she is a fabric designer first and foremost, and as such a lot of her patterns call for a huge amount of wastage. her placement of the pattern peices is not always worth following.
oh, and one more thing, the size of the hood she suggests is way too small IMHO, so i increased it on this one.
Dont get me wrong though, i LUUUUUUUURVE Amy Butler, and i think all her designs and patterns are fabulous. as with everything, we all have our own little tweaks on things ;-)