diff --git a/spec/plugins/dry_validation_spec.rb b/spec/plugins/dry_validation_spec.rb
index ea857ea..be91aba 100644
--- a/spec/plugins/dry_validation_spec.rb
+++ b/spec/plugins/dry_validation_spec.rb
@@ -174,6 +174,24 @@ class OperationWithAutoWire < Operation
               .to include(:gender)
           end
         end
+
+        context "when called with no block nor contract" do
+          subject(:opr_class) { Class.new(Operation) { plugin :dry_validation } }
+
+          it 'raises an error' do
+            expect { opr_class.contract }.to raise_error(ArgumentError, 'Either a contract class or a block must be provided')
+          end
+        end
+
+        context 'when the operation is inherited' do
+          let(:opr_class) { OperationWithAutoWire }
+          subject(:opr_subclass) { Class.new(OperationWithAutoWire) }
+
+          it "sets 'contract_class' and 'auto_wire' from the superclass", :aggregate_failures do
+            expect(opr_subclass.auto_wire).to eq(opr_class.auto_wire)
+            expect(opr_subclass.contract_class).to eq(opr_class.contract_class)
+          end
+        end
       end
 
       describe "#call" do
diff --git a/spec/plugins/sequel_models_spec.rb b/spec/plugins/sequel_models_spec.rb
index 1be2a36..29d4e25 100644
--- a/spec/plugins/sequel_models_spec.rb
+++ b/spec/plugins/sequel_models_spec.rb
@@ -58,8 +58,6 @@ def chain_operation(state)
         end
       end
 
-      class SubOperation < MyOperation; end
-
       describe 'DSL' do
         let(:result) { operation.call(params) }
         let(:params) { { email: 'asd@fgh.net' } }
@@ -274,13 +272,14 @@ class InvalidOperation < MyOperation
         end
 
         context 'when the operation is inherited' do
-          it "sets 'result_key', 'search_field', 'model_class' and 'model_not_found' from the superclass" do
-            aggregate_failures do
-              expect(SubOperation.result_key).to eq(MyOperation.result_key)
-              expect(SubOperation.search_field).to eq(MyOperation.search_field)
-              expect(SubOperation.model_class).to eq(MyOperation.model_class)
-              expect(SubOperation.model_not_found).to eq(MyOperation.model_not_found)
-            end
+          let(:opr_class) { MyOperation }
+          subject(:opr_subclass) { Class.new(opr_class) }
+
+          it "sets 'result_key', 'search_field', 'model_class' and 'model_not_found' from the superclass", :aggregate_failures do
+            expect(opr_subclass.result_key).to eq(opr_class.result_key)
+            expect(opr_subclass.search_field).to eq(opr_class.search_field)
+            expect(opr_subclass.model_class).to eq(opr_class.model_class)
+            expect(opr_subclass.model_not_found).to eq(opr_class.model_not_found)
           end
         end
       end