This looks like a duplicate of Re-download a SNAPSHOT version of a dependency using SBT. However, the comments there say that
There is no need to mark SNAPSHOT dependencies as changing() because sbt configures Ivy to know this already.
I am using SBT 1.9.7, and perhaps sbt is telling Ivy, but I am clearly seeing it reference an out-of-date jar after test and then show externalDependencyClasspath. The jar is in the ~/Library/Caches/Coursier/v1/https/, so perhaps Coursier does not support this or the Ivy configuration code never got applied to Coursier.
In fact, I am finding it nearly impossible to get sbt to use the newest version of the dependency. I have deleted the directory in the cache, added and removed changing() from the dependency statement, run sbt update several times, and it is still referencing the old jar.
I looked at the Nexus server in a browser and the new version is there, right alongside the old version.
How do I get it to download the new version of the snapshot?
The sledgehammer solution that I found is to do this:
In sbt, run
show externalDependencyClasspath
lastGrep <name of your jar>
That shows all of the dependencies and then filters the output down a something that is manageable in size.
Next, exit sbt and delete the cache. On a Mac, I found that
rm -rf ~/Library/Caches/Coursier/v1/https/<repo-host>/repository/<group-and-artifact-id>
was a reasonable level to delete.
After that, when I started sbt, it would re-download the jar and get the latest version.