SCHWED-776: extended set of unit tests for modelling of oligomers.

modelling/doc/index.rst

modelling/pymod/_closegaps.py

modelling/tests/CMakeLists.txt

modelling/tests/data/2jlp-1.fasta

modelling/tests/data/2jlp-1.pdb

modelling/tests/data/hetero-punched.pdb

modelling/tests/test_close_gaps.py

modelling/tests/test_modelling.py

modelling/tests/test_pipeline.py

modelling/tests/test_ring_punches.py