stub: add spec for stub-first stub zone option

Add a spec test for the newly introduced stub-first option.

Author: Alexandros Afentoulis

spec/defines/stub_spec.rb

@@ -77,6 +77,29 @@
         }
       end
 
+      context 'with stub_first set' do
+        let(:params) do
+          {
+            address: ['::1'],
+            stub_first: true
+          }
+        end
+
+        it { is_expected.to compile.with_all_deps }
+        it { is_expected.to contain_unbound__stub('lab.example.com') }
+
+        it {
+          expect(subject).to contain_concat__fragment('unbound-stub-lab.example.com').with(
+            content: <<~ZONE
+              stub-zone:
+                name: "lab.example.com"
+                stub-addr: ::1
+                stub-first: yes
+            ZONE
+          )
+        }
+      end
+
       context 'with address set as string' do
         let(:params) do
           {