Set expected list of elements for Parmed PSF test

[IAlibay]

Fixes #4015

Changes made in this Pull Request:

• Add a list of expected elements rather than just empty strings

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[codecov]

Codecov Report

Base: 93.52% // Head: 93.52% // No change to project coverage 👍

Coverage data is based on head (c7b0707) compared to base (d73523f).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4016   +/-   ##
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  Coverage    93.52%   93.52%           
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  Files          190      190           
  Lines        25028    25028           
  Branches      3542     3542           
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  Hits         23407    23407           
  Misses        1100     1100           
  Partials       521      521           

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[IAlibay]

@MDAnalysis/coredevs can I get a quick check here - this issue is making CI fail across the board.

[orbeckst]

lgtm

Is there anything in the docs that we need to add about new capabilities?

Do we need to restrict to newer versions of parmed or is the new capability just incidental and it doesn't really matter to us?

[IAlibay]

lgtm

Is there anything in the docs that we need to add about new capabilities?

Do we need to restrict to newer versions of parmed or is the new capability just incidental and it doesn't really matter to us?

@orbeckst It's purely incidental & only affects tests - i.e. upstream now supports it so if you use the latest parmed you'll get elements instead of empty strings. Otherwise you'll get empty strings (i.e. the expected behaviour before the previous release).

I've clarified this in the changelog.