test: Improve ComposablePass tests (#2688)

Suggestion missing from #2636, makes sure we test the actual
implementation rather than the dummy one.

drive-by: Improve `name` impl for ComposedPass

Author: aborgna-q

hugr-py/src/hugr/passes/_composable_pass.py

@@ -52,3 +52,7 @@ def __call__(self, hugr: Hugr):
         """Call all of the passes in sequence."""
         for comp_pass in self.passes:
             comp_pass(hugr)
+
+    @property
+    def name(self) -> str:
+        return f"Composed({ ', '.join(pass_.name for pass_ in self.passes) })"

hugr-py/tests/test_passes.py

@@ -7,20 +7,20 @@ class MyDummyPass(ComposablePass):
         def __call__(self, hugr: Hugr) -> None:
             return self(hugr)
 
-        def then(self, other: ComposablePass) -> ComposablePass:
-            return ComposedPass([self, other])
-
-        @property
-        def name(self) -> str:
-            return "Dummy"
-
     dummy = MyDummyPass()
 
-    composed = dummy.then(dummy)
+    composed_dummies = dummy.then(dummy)
 
     my_composed_pass = ComposedPass([dummy, dummy])
-
     assert my_composed_pass.passes == [dummy, dummy]
-    assert isinstance(my_composed_pass, ComposablePass)
-    assert isinstance(composed, ComposablePass)
-    assert dummy.name == "Dummy"
+
+    assert isinstance(composed_dummies, ComposablePass)
+    assert composed_dummies == my_composed_pass
+
+    assert dummy.name == "MyDummyPass"
+    assert composed_dummies.name == "Composed(MyDummyPass, MyDummyPass)"
+
+    assert (
+        composed_dummies.then(my_composed_pass).name
+        == "Composed(MyDummyPass, MyDummyPass, MyDummyPass, MyDummyPass)"
+    )