Pointing this argument at a tmpfs filesystem can improve the
speed of the test suite for some users.
+Certain tests require precomputed databases to complete. You can fetch these
+databases with
+
+ make download-test-databases
+
+If you do not download the test databases, the relevant tests will be
+skipped.
+
When invoking the test suite via "make test" any of the above options
can be specified as follows: