know if a zone exist at a specific date

app/models/zone.rb

@@ -23,4 +23,8 @@ class Zone < ApplicationRecord
       date >= designated_on
     end.at(1)
   end
+
+  def available_at?(date)
+    label_at(date) != 'NA'
+  end
 end

spec/models/zone_spec.rb

@@ -34,5 +34,36 @@ describe Zone do
       expect(zone.label_at(start_previous_government - 1.week)).to eq "Ministère de l'Économie, des Finances et de la Relance"
     end
   end
+
+  describe "#available_at?" do
+    let(:start_previous_government) { Date.parse('2020-07-06') }
+    let(:start_last_government) { Date.parse('2022-05-20') }
+    let(:start_futur_government) { Date.parse('2027-05-20') }
+    let(:zone) do
+      create(:zone, labels: [
+        {
+          designated_on: start_previous_government,
+          name: "Ministère des Outre-mer"
+        },
+        {
+          designated_on: start_last_government,
+          name: "NA"
+        },
+        {
+          designated_on: start_futur_government,
+          name: "Ministère des Territoires d'Outre-mer"
+        }
+      ])
+    end
+
+    it "returns false if the zone does'nt exist at a specific date" do
+      expect(zone.available_at?(start_last_government + 1.week)).to be_falsy
+    end
+
+    it "returns true if the zone exist at a specific date" do
+      expect(zone.available_at?(start_futur_government + 1.week)).to be_truthy
+      expect(zone.available_at?(start_previous_government + 1.week)).to be_truthy
+    end
+  end
 end