Re: regression tests for `lilypond-book`?

[Werner LEMBERG]

>> ... it doesn't do a comparison against correct input.
> 
> The lilypond-book directory tests features of lilypond-book, but it
> doesn't any real comparison. Meaningful comparison would be to compare
> PDF files (after processing with LaTeX) across versions,

I disagree.  There are two issues that should be tested.

* Check whether PDFs (and other output formats) can be actually
  generated.  AFAICS, this is what the current tests do.

* Process the test input files with the current `lilypond-book`
  version, check its output for correctness (including manual
  compilation with LilyPond so that the PDFs can be inspected *once*),
  then store the output files from lilypond-book – and only from
  lilypond-book, without calling LilyPond – as a baseline.

  Newer versions simply compare its output against this baseline.


    Werner