messagerie: better format message dates

spec/helpers/commentaire_helper_spec.rb

@@ -18,4 +18,34 @@ RSpec.describe CommentaireHelper, type: :helper do
       it { is_expected.to eq nil }
     end
   end
+
+  describe '.commentaire_date' do
+    let(:present_date) { Time.local(2018, 9, 2, 10, 5, 0) }
+    let(:creation_date) { present_date }
+    let(:commentaire) do
+      Timecop.freeze(creation_date) { create(:commentaire, email: "michel@pref.fr") }
+    end
+
+    subject do
+      Timecop.freeze(present_date) { commentaire_date(commentaire) }
+    end
+
+    it 'doesn’t include the creation year' do
+      expect(subject).to eq 'le 2 septembre à 10 h 05'
+    end
+
+    context 'when displaying a commentaire created on a previous year' do
+      let(:creation_date) { present_date.prev_year }
+      it 'includes the creation year' do
+        expect(subject).to eq 'le 2 septembre 2017 à 10 h 05'
+      end
+    end
+
+    context 'when formatting the first day of the month' do
+      let(:present_date) { Time.local(2018, 9, 1, 10, 5, 0) }
+      it 'includes the ordinal' do
+        expect(subject).to eq 'le 1er septembre à 10 h 05'
+      end
+    end
+  end
 end