ShowGroup now validates output correctly

app/interactors/show_group.rb

@@ -4,6 +4,10 @@ def validate_input
   end
 
   def execute
-    context.group = Group.find(context.id)
+    context.group = Group.find_by(id: context.id)
+  end
+
+  def validate_output
+    context.fail!(errors: "invalid output") unless context.group
   end
 end

spec/interactors/show_group_spec.rb

@@ -1,6 +1,6 @@
 RSpec.describe ShowGroup do
   describe ".call" do
-    let(:group) { create(:group) }
+    let(:group) { create(:group, id: 876) }
 
     context "when successful" do
       subject do
@@ -29,5 +29,19 @@
         expect(subject.errors).to eq("invalid input")
       end
     end
+
+    context "when a Group was not found" do
+      subject do
+        described_class.call(id: 9999)
+      end
+
+      it "fails" do
+        is_expected.to be_a_failure
+      end
+
+      it "returns an error" do
+        expect(subject.errors).to eq("invalid output")
+      end
+    end
   end
 end