I had one case these days in which I also had a lot of data to use in the test. I was able to put the data as very large regular D arrays, but this increased my compilation times a lot (not to mention the time to run the unit tests).
I decided to enclose this specific unit test (including the `import test_data` statement) in `version ExtraUnitTests { ... }`. This way, I can run the bulk of my unit tests very frequently without wasting time with this special case I want to run only sometimes.
I can't say I am 100% happy with this, but it worked for me and didn't require any additional dependency.
LMB