General correctness tests

[tikitu]

We can make a pretty good test for general correctness as follows: for each one of a number of real JS files (the kind of thing that people want to minify):

1. Make file.min.js with jsmin.
2. Make file.othermin.js with some other minifying tool.
3. Make file.min.othermin.js using the other minifying tool, starting with the jsmin minified file.

If jsmin is doing its job right, the two othermin files should be identical.

[tikitu]

Could also run jshint or similar on the result, checking for fatal errors.