add test case to geometry read/write

tests/test_data.py

@@ -166,6 +166,20 @@ def test_readwrite_cycle(dataset, tmp_path):
         geometry.per_atom.numbers,
         np.array([6, 8, 9]),
     )
+    s = """7
+
+O       0.269073490000000      0.952731530000000      0.639899630000000
+C       0.379007320000000     -0.130111590000000      0.085677050000000
+C      -0.611025150000000     -0.821472640000000     -0.827555540000000
+H       1.276678450000000     -0.822788000000000      0.432385510000000
+H      -0.364845780000000     -1.985677100000000     -0.791238000000000
+H      -1.419992260000000     -0.472979080000000     -0.156752270000000
+H      -0.764765500000000     -0.536376480000000     -1.844856190000000
+"""
+    geometry = Geometry.from_string(s)
+    assert not geometry.periodic
+    assert len(geometry) == 7
+    assert geometry.energy is None
 
 
 def test_dataset_empty(tmp_path):