[unittests] Add test for mechanism reduction

test/python/test_kinetics.py

@@ -304,7 +304,7 @@ def test_coverage_dependence_flags(self):
         surf.net_rates_of_progress_ddCi
 
     def test_electrochemistry_flags(self):
-             # Phases
+        # Phases
         mech = "lithium_ion_battery.yaml"
         anode, cathode, metal, electrolyte = ct.import_phases(
             mech, ["anode", "cathode", "electron", "electrolyte"])
@@ -315,6 +315,29 @@ def test_electrochemistry_flags(self):
         anode_int.derivative_settings = {"skip-electrochemistry": True}
         anode_int.net_rates_of_progress_ddCi
 
+    def test_submechanism(self):
+        # Simplified samples/python/kinetics/extract_submechanism.py
+        gri30 = ct.Solution('gri30.yaml')
+        h2o2 = ct.Solution('h2o2.yaml')
+
+        reactions = []
+        dest_species = set(h2o2.species_names)
+        colliders = dest_species.union([None, "M"])
+        for R in gri30.reactions():
+            if all(S in dest_species for S in (R.reactants | R.products).keys()):
+                if R.third_body_collider in colliders:
+                    reactions.append(R)
+
+        gas = ct.Solution(thermo='ideal-gas', kinetics='gas', species=h2o2.species(),
+                          reactions=reactions)
+        assert gas.n_reactions == len(reactions)
+        assert gas.n_species == len(h2o2.species_names)
+
+        gas.write_yaml("reduced.yaml")
+        restored = ct.Solution("reduced.yaml")
+        assert gas.species_names == restored.species_names
+        assert gas.reaction_equations() == restored.reaction_equations()
+
 
 class KineticsRepeatability(utilities.CanteraTest):
     """