Fix unit tests for: Don't UNMARK duplicate reactions so aggressively.

The new code doesn't remove duplicate reaction marks, so 
this test is marked as a work in progress.

Unless we decide the current behavior is ideal, in which case
we can change the expected outcomes and make this pass.

rmgpy/chemkinTest.py

@@ -411,6 +411,21 @@ def test_mark_duplicate_reactions(self):
 
         self.assertEqual(duplicate_flags, expected_flags)
 
+    @work_in_progress
+    def test_unmark_duplicate_reactions(self):
+        """Test that we can properly REMOVE duplicate reaction flags for Chemkin."""
+
+        """
+        We can't do this properly yet. 
+        See https://github.com/ReactionMechanismGenerator/RMG-Py/pull/1856
+        """
+        s1 = Species().from_smiles('CC')
+        s2 = Species().from_smiles('[CH3]')
+        s3 = Species().from_smiles('[OH]')
+        s4 = Species().from_smiles('C[CH2]')
+        s5 = Species().from_smiles('O')
+        s6 = Species().from_smiles('[H]')
+
         # Try initializing with duplicate=True
         reaction_list = [
             Reaction(reactants=[s1], products=[s2, s2], duplicate=True, kinetics=Arrhenius()),
@@ -423,6 +438,8 @@ def test_mark_duplicate_reactions(self):
             Reaction(reactants=[s3, s6], products=[s5], duplicate=True, kinetics=Arrhenius(), reversible=False),
         ]
 
+        expected_flags = [True, True, False, False, True, True, False, False]
+
         mark_duplicate_reactions(reaction_list)
         duplicate_flags = [rxn.duplicate for rxn in reaction_list]