Today I learned that if you need to test in older versions of Chrome then you can download prior snapshots of Chromium builds as standalone executables.
The tricky part is figuring out which build snapshot corresponds to which version of Chrome, which involves several steps detailed in the Chromium wiki.
Fortunately, someone put together a site to lookup by Chrome version and link to the correct build on the archive site.
Then you download and extract the zip file and run the single executable, i.e. chrome.exe.