MakeMaker assumes that you want to run all of the .t files in the t/
directory in ascii-betical order during make test unless you say
otherwise. This leads to some interesting naming schemes for test
files to get them in the desired order.
You can specify any order or any files that you like, though, with the
test directive to WriteMakefile.
Test::Manifest looks in the t/test_manifest file to find out which
tests you want to run and the order in which you want to run them. It
constructs the right value for MakeMaker to do the right thing.