diff --git a/tests/test_dagset.py b/tests/test_dagset.py
index cf53177..43798bc 100644
--- a/tests/test_dagset.py
+++ b/tests/test_dagset.py
@@ -89,32 +89,59 @@ class TestDAGSetBasicOps:
 class TestDAGSetCallbacks:
     """Test callback mechanisms."""
 
-    def test_on_add_callback(self) -> None:
-        added: list[int] = []
-        s = DAGSetView({1, 2})
-        s.on_add = lambda v: added.append(v)
-        s.add(3)
-        assert 3 in added
-        assert len(added) == 1
+    class TestBasicOps:
+        def test_on_add_callback(self) -> None:
+            added: list[int] = []
+            s = DAGSetView({1, 2})
+            s.on_add = lambda v: added.append(v)
+            s.add(3)
+            assert 3 in added
+            assert len(added) == 1
 
-    def test_on_remove_callback(self) -> None:
-        removed: list[int] = []
-        s = DAGSetView({1, 2, 3})
-        s.on_remove = lambda v: removed.append(v)
-        s.discard(2)
-        assert 2 in removed
-        assert len(removed) == 1
+        def test_on_remove_callback(self) -> None:
+            removed: list[int] = []
+            s = DAGSetView({1, 2, 3})
+            s.on_remove = lambda v: removed.append(v)
+            s.discard(2)
+            assert 2 in removed
+            assert len(removed) == 1
+
+        def test_callbacks_none_by_default(self) -> None:
+            s = DAGSetView()
+            assert s.on_add is None
+            assert s.on_remove is None
+
+    class TestInPlaceOperators:
+        def test_ior_triggers_callbacks(self) -> None:
+            added: list[int] = []
+            s = DAGSetView({1})
+            s.on_add = lambda v: added.append(v)
+            s |= {2, 3}
+            assert 2 in added
+            assert 3 in added
+
+        def test_iadd_triggers_callbacks(self) -> None:
+            added: list[int] = []
+            s = DAGSetView({1})
+            s.on_add = lambda v: added.append(v)
+            s += [2, 3]
+            assert 2 in added
+            assert 3 in added
+
+        def test_isub_triggers_callbacks(self) -> None:
+            removed: list[int] = []
+            s = DAGSetView({1, 2, 3})
+            s.on_remove = lambda v: removed.append(v)
+            s -= {2, 3}
+            assert 2 in removed
+            assert 3 in removed
 
-    def test_callbacks_none_by_default(self) -> None:
-        s = DAGSetView()
-        assert s.on_add is None
-        assert s.on_remove is None
 
 
 class TestDAGSetInPlaceOperators:
     """Test in-place set operators."""
 
-    class TestDAGSetIOR:
+    class TestIOR:
         def test_set(self) -> None:
             s = DAGSetView({1, 2})
             s |= {3, 4}
@@ -130,86 +157,56 @@ class TestDAGSetInPlaceOperators:
             s |= "xyz"
             assert "xyz" in s
 
-    class TestDAGSetIAdd:
-        pass
+    class TestIAdd:
+        def test_set(self) -> None:
+            s = DAGSetView({1, 2})
+            s += {3, 4}
+            assert set(s) == {1, 2, 3, 4}
 
-    class TestDAGSetISub:
-        pass
+        def test_list(self) -> None:
+            s = DAGSetView({1})
+            s += [2, 3]
+            assert set(s) == {1, 2, 3}
 
-    def test_iadd_with_set(self) -> None:
-        s = DAGSetView({1, 2})
-        s += {3, 4}
-        assert set(s) == {1, 2, 3, 4}
+        def test_string(self) -> None:
+            s = DAGSetView({"a"})
+            s += "b"
+            assert "b" in s
 
-    def test_iadd_with_list(self) -> None:
-        s = DAGSetView({1})
-        s += [2, 3]
-        assert set(s) == {1, 2, 3}
+    class TestISub:
+        def test_set(self) -> None:
+            s = DAGSetView({1, 2, 3, 4})
+            s -= {2, 3}
+            assert set(s) == {1, 4}
 
-    def test_iadd_with_string(self) -> None:
-        s = DAGSetView({"a"})
-        s += "b"
-        assert "b" in s
+        def test_list(self) -> None:
+            s = DAGSetView({1, 2, 3})
+            s -= [2]
+            assert set(s) == {1, 3}
 
-    def test_isub_with_set(self) -> None:
-        s = DAGSetView({1, 2, 3, 4})
-        s -= {2, 3}
-        assert set(s) == {1, 4}
+        def test_string(self) -> None:
+            s = DAGSetView({"a", "b", "c"})
+            s -= "b"
+            assert set(s) == {"a", "c"}
 
-    def test_isub_with_list(self) -> None:
-        s = DAGSetView({1, 2, 3})
-        s -= [2]
-        assert set(s) == {1, 3}
+    class TestIAnd:
+        def test_set(self) -> None:
+            s = DAGSetView({1, 2, 3})
+            s &= {2, 3, 4}
+            assert set(s) == {2, 3}
 
-    def test_isub_with_string(self) -> None:
-        s = DAGSetView({"a", "b", "c"})
-        s -= "b"
-        assert set(s) == {"a", "c"}
+        def test_list(self) -> None:
+            s = DAGSetView({1, 2, 3})
+            s &= [2, 3]
+            assert set(s) == {2, 3}
 
-    def test_iand_with_set(self) -> None:
-        s = DAGSetView({1, 2, 3})
-        s &= {2, 3, 4}
-        assert set(s) == {2, 3}
+    class TestIXor:
+        def test_set(self) -> None:
+            s = DAGSetView({1, 2, 3})
+            s ^= {3, 4, 5}
+            assert set(s) == {1, 2, 4, 5}
 
-    def test_iand_with_list(self) -> None:
-        s = DAGSetView({1, 2, 3})
-        s &= [2, 3]
-        assert set(s) == {2, 3}
-
-    def test_ixor_with_set(self) -> None:
-        s = DAGSetView({1, 2, 3})
-        s ^= {3, 4, 5}
-        assert set(s) == {1, 2, 4, 5}
-
-    def test_ixor_with_list(self) -> None:
-        s = DAGSetView({1, 2})
-        s ^= [2, 3]
-        assert set(s) == {1, 3}
-
-
-class TestDAGSetCallbacksWithOperators:
-    """Test that callbacks fire with in-place operators."""
-
-    def test_ior_triggers_callbacks(self) -> None:
-        added: list[int] = []
-        s = DAGSetView({1})
-        s.on_add = lambda v: added.append(v)
-        s |= {2, 3}
-        assert 2 in added
-        assert 3 in added
-
-    def test_iadd_triggers_callbacks(self) -> None:
-        added: list[int] = []
-        s = DAGSetView({1})
-        s.on_add = lambda v: added.append(v)
-        s += [2, 3]
-        assert 2 in added
-        assert 3 in added
-
-    def test_isub_triggers_callbacks(self) -> None:
-        removed: list[int] = []
-        s = DAGSetView({1, 2, 3})
-        s.on_remove = lambda v: removed.append(v)
-        s -= {2, 3}
-        assert 2 in removed
-        assert 3 in removed
+        def test_list(self) -> None:
+            s = DAGSetView({1, 2})
+            s ^= [2, 3]
+            assert set(s) == {1, 3}