Add strong stationarity property to DualProj

Author: PierreQuinton

tests/unit/aggregation/test_dualproj.py

@@ -7,12 +7,16 @@
     ExpectedStructureProperty,
     NonConflictingProperty,
     PermutationInvarianceProperty,
+    StrongStationarityProperty,
 )
 
 
 @mark.parametrize("aggregator", [DualProj()])
 class TestDualProj(
-    ExpectedStructureProperty, NonConflictingProperty, PermutationInvarianceProperty
+    ExpectedStructureProperty,
+    NonConflictingProperty,
+    PermutationInvarianceProperty,
+    StrongStationarityProperty,
 ):
     pass