When trying out new stuff in sewing, including patterns, which never fit without adjustments, since none of us fit manufacturers' "standards," here's a quote from my favorite dressmaker's guide that says it all. It applies to any kind of sewing, not just 19th century women's wear, and these days the fabric is more like $30/yard.
If you do not make a muslin [or other very cheap fabric] version of a new pattern, it is quite likely that an entire civilization will be wiped out by meteors. Plague and pestilence will cover the land. Sheep will begin to shrink in the rain. Butter will go rancid.
Right, so things won't be quite that desperate. But, the possibility of enormous stress and tension when your project doesn't look well and you just ruined your $20/yard silk--that's a very real possibility if you skip the 20 minute, $2 step of making a test version of the bodice and one sleeve, and basting them together to test the fit and functionality.
--Elizabeth Stewart Clark, The Dressmaker's Guide: 1840-1865
, Second Edition. Heide Press, Inc., 2009, p. 207.