Adds test to make sure small box issue is now fixed #2670

[IAlibay]

Fixes #2670

Changes made in this Pull Request:

• Adds the one test from @richardjgowers

PR Checklist

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

[codecov]

Codecov Report

Merging #3163 (9fd5e05) into master (7ed893d) will increase coverage by 0.84%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3163      +/-   ##
==========================================
+ Coverage   90.97%   91.81%   +0.84%     
==========================================
  Files         162      167       +5     
  Lines       22194    22699     +505     
  Branches     3198     3198              
==========================================
+ Hits        20190    20841     +651     
- Misses       1381     1774     +393     
+ Partials      623       84     -539     

Impacted Files	Coverage Δ
package/MDAnalysis/topology/tpr/obj.py	96.82% <0.00%> (-3.18%)	⬇️
...onality_reduction/DimensionalityReductionMethod.py	97.14% <0.00%> (-2.86%)	⬇️
package/MDAnalysis/due.py	56.09% <0.00%> (ø)
package/MDAnalysis/analysis/legacy/x3dna.py	0.00% <0.00%> (ø)
package/MDAnalysis/analysis/legacy/__init__.py	0.00% <0.00%> (ø)
package/MDAnalysis/tests/__init__.py	100.00% <0.00%> (ø)
package/MDAnalysis/tests/datafiles.py	31.25% <0.00%> (ø)
package/MDAnalysis/core/selection.py	99.52% <0.00%> (+<0.01%)	⬆️
...sis/analysis/encore/clustering/ClusteringMethod.py	96.96% <0.00%> (+0.04%)	⬆️
package/MDAnalysis/analysis/base.py	95.60% <0.00%> (+0.04%)	⬆️
... and 85 more

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