user2119: I'm interested to test that the atom syntax highlighter for pgn files -- https://atom.io/packages/language-pgn -- can handle the full range of possible files.  Is there a suite of difficult test files somewhere?  
Also related might be this question:
What are all of the possible tags for PGN?

user12951: As an author of some PGN-processing software, I would also be interested in having access to a general test suite but I am not aware of any, unfortunately, and all I can offer is some advice based on experience.
I would be wary of throwing a large database of games at an application in order to test it before you have developed reasonable confidence with its fundamentals. In the early stages, at least, I find it most effective to create a lot of small examples, each of which tests an individual feature. That way, errors are relatively easy to spot because they don't get lost in a mass of output. Once I have got rid of the basic errors I would then look at combining a small number of both related and unrelated features in individual tests to make sure that there is no unexpected interference between the associated functionality. Only late on would I switch to large datasets to make sure there are no issues with scaling up.
I also highly recommend re-running all the existing tests each time a new feature is added. I have been amazed how often I have unexpectedly broken something seemingly unrelated as the code has developed.
Apologies if these principles are already well known to you!

2119: <p>I'm interested to test that the atom syntax highlighter for pgn files -- <a href="https://atom.io/packages/language-pgn" rel="nofollow noreferrer">https://atom.io/packages/language-pgn</a> -- can handle the full range of possible files.  Is there a suite of difficult test files somewhere?  </p>

<p>Also related might be this question:</p>

<p><a href="https://chess.stackexchange.com/questions/15575/what-are-all-of-the-possible-tags-for-pgn">What are all of the possible tags for PGN?</a></p>
 12951: <p>As an author of some PGN-processing software, I would also be interested in having access to a general test suite but I am not aware of any, unfortunately, and all I can offer is some advice based on experience.</p>

<p>I would be wary of throwing a large database of games at an application in order to test it before you have developed reasonable confidence with its fundamentals. In the early stages, at least, I find it most effective to create a lot of small examples, each of which tests an individual feature. That way, errors are relatively easy to spot because they don't get lost in a mass of output. Once I have got rid of the basic errors I would then look at combining a small number of both related and unrelated features in individual tests to make sure that there is no unexpected interference between the associated functionality. Only late on would I switch to large datasets to make sure there are no issues with scaling up.</p>

<p>I also highly recommend re-running all the existing tests each time a new feature is added. I have been amazed how often I have unexpectedly broken something seemingly unrelated as the code has developed.</p>

<p>Apologies if these principles are already well known to you!</p>
