Add test_deterministic_bicyclic_decomposition

Test that the decomposition of a polyring into bicyclics and then into single rings
is deterministic. This is important because the thermo estimation depends on the
order of the rings. Currently this is not guaranteed, so if this test fails, we
just skip it.

See #2562

Author: rwest

test/rmgpy/data/thermoTest.py

@@ -2272,6 +2272,32 @@ def test_bicyclic_decomposition_for_polyring_using_alkane_tricyclic(self):
         expected_aromatic_bond_num_in_bicyclics = [0, 0, 0]
         assert aromatic_bond_num_in_bicyclics == expected_aromatic_bond_num_in_bicyclics
 
+    def test_deterministic_bicyclic_decomposition(self):
+        """
+        Test that the decomposition of a polyring into bicyclics and then into single rings
+        is deterministic. This is important because the thermo estimation depends on the
+        order of the rings. Currently this is not guaranteed, so if this test fails, we
+        just skip it. 
+        
+        See https://github.com/ReactionMechanismGenerator/RMG-Py/issues/2562
+        """
+        mol = Molecule(smiles="C1=CC2C=CC=1C=C2")
+        polyrings = mol.get_disparate_cycles()[1]
+        assert len(polyrings) == 1
+        assert rmgpy.data.thermo.is_bicyclic(polyrings[0])
+        polyring = polyrings[0]
+        submol = rmgpy.data.thermo.convert_ring_to_sub_molecule(polyring)[0]
+        rings = rmgpy.data.thermo.split_bicyclic_into_single_rings(submol)
+        assert len(rings) == 2
+        ring_smiles = [ring.to_smiles() for ring in rings]
+        for smiles in ring_smiles:
+            assert smiles in ["C1C=CC=C=C1", "C1C=CCC=C1"]
+        # Ensure that the order is the same every time
+        try:
+            assert ring_smiles == ["C1C=CC=C=C1", "C1C=CCC=C1"]
+        except AssertionError as e:
+            pytest.skip(f"Skipping because not yet deterministic (#2562): {e}")
+
     def test_combine_cycles(self):
         """
         This method tests the combine_cycles method, which simply joins two lists