The test files are ordered thus:

0** - basic and non-compile-based tests
1** - compile-based tests
2** - Perl package tests
3** - other package tests
4** - tests of other functionality

0-level tests do not require any sort of compilation or interaction with the
compiled code. They look like normal Perl tests.

100-level tests require interaction with compiled code, but cannot invoke any
packages. Since TCC::Perl is a package, this means that the only interaction
is via printing to stdout. As such, all 100-level tests invoke code that
communicates via C printf's, and use inc::Capture to get the results.

200-level tests focus exclusively on the TCC::Perl package.

300-level tests focus on the other included packages. They can interact with
the perl interpreter via TCC::Perl, since that will already have been
tested by the time these run.

400-level tests are for other submodules of the library.
