These will be helpful for catching regressions or changes in behavior
to edge cases such as empty input, or specifically crafted inputs that
may cause panics, etc.
Move test for issue #172 there since it's a document-level test, not an
inline one.
Add test for issue #173.
Make some things more consistent.
Don't use a named receiver in methods that don't use it. This makes the
code more readable since one can more quickly tell the inputs to the
method.
