Added test for issue #13

crystals/__init__.py

@@ -5,7 +5,7 @@
 __author__ = "Laurent P. René de Cotret"
 __email__ = "laurent.renedecotret@mail.mcgill.ca"
 __license__ = "GPLv3"
-__version__ = "1.6.0"
+__version__ = "1.6.1"
 
 from .atom import Atom
 from .atom import Element

crystals/tests/test_writers.py

@@ -3,11 +3,11 @@
 import tempfile
 from itertools import islice
 from pathlib import Path
-from random import choice, randint
-
 import numpy as np
+from tempfile import TemporaryDirectory
+
 import pytest
-from crystals import Crystal
+from crystals import Crystal, Atom
 
 try:
     import ase
@@ -53,6 +53,26 @@ def test_cif_writer_idempotence(name):
         assert cryst == cryst2
 
 
+def test_supercell_preserved_in_cif():
+    """See issue #13."""
+    a = np.asfarray([3, 0.2, 0])
+    b = np.asfarray([0.4, 8, 0])
+    c = np.asfarray([0, 0, 9])
+
+    dimer = Crystal(
+        unitcell=[Atom("C", coords=(0.5, 0, 0)), Atom("C", coords=(0, 0, 0))],
+        lattice_vectors=[a * 2, b, c],
+    )
+    with TemporaryDirectory() as tmpdir:
+
+        dimer.to_cif(Path(tmpdir) / "dimer.cif")
+        from_file = Crystal.from_cif(Path(tmpdir) / "dimer.cif")
+
+    assert set(tuple(atm.coords_fractional) for atm in dimer.unitcell) == set(
+        tuple(atm.coords_fractional) for atm in from_file.unitcell
+    )
+
+
 @pytest.mark.parametrize("name", Crystal.builtins)
 def test_vasp_writer_idempotence(name):
     """Test that conversion to VASP of a structure loaded from VASP is idempotent."""