This file describes tests that might be useful to implement.

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lyx2lyx tests

One way to implemente tests of lyx2lyx is to do a roundtrip lyx2lyx
conversion (e.g. with the previous major release format) and then compare the
exported .tex files before and after. Ideally there should be no change.

Georg detailed a clearly better idea, but would take more time to implement:

  If you want to test lyx2lyx, then I would strongly advise to test lyx2lyx
  alone, without LyX. This would be exactly the same procedure as we do with
  tex2lyx: For each test case, keep the expected output of lyx2lyx as
  reference, and verify once (when creating the test), that LyX will produce
  the correct output. When testing, do only compare the lyx2lyx output against
  the refernce. If you keep LyX (and even pdflatex) in the chain, then you
  will be testing lyx2lyx, LyX and pdflatex at the same time, which will
  increase the probability of failing tests, and the search for the cause will
  be more difficult.
    
  Finally I have a general remark: The forward conversion in lyx2lyx is much
  more important than the backward conversion, and the only one we guarantee
  to work for each format step. The backward conversion is only implemented
  for those cases where it is possible with reasonable effort. If we start to
  test lyx2lyx, then we should start with the forward conversion.

For (possibly) more discussion, see:
https://www.mail-archive.com/search?l=mid&q=n15uao%24upk%241%40ger.gmane.org
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