Add spec for CountriesAndCities service

spec/services/countries_and_cities_spec.rb

@@ -0,0 +1,30 @@
+require 'rails_helper'
+
+RSpec.describe CountriesAndCities do
+  describe '#call' do
+    subject(:countries_and_cities) { described_class.new(points).call }
+
+    let(:points) do
+      [
+        create(:point, latitude: 0, longitude: 0, city: 'City', country: 'Country'),
+        create(:point, latitude: 1, longitude: 1, city: 'City', country: 'Country'),
+        create(:point, latitude: 2, longitude: 2, city: 'City', country: 'Country'),
+        create(:point, latitude: 2, longitude: 2, city: 'Another city', country: 'Some Country'),
+        create(:point, latitude: 2, longitude: 6, city: 'Another city', country: 'Some Country')
+      ]
+    end
+
+    before do
+      stub_const('CountriesAndCities::MINIMUM_POINTS_IN_CITY', 1)
+    end
+
+    it 'returns countries and cities' do
+      expect(countries_and_cities).to eq(
+        [
+          { cities: [{city: "City", points: 3, timestamp: 1}], country: "Country" },
+          { cities: [{city: "Another city", points: 2, timestamp: 1}], country: "Some Country" }
+        ]
+      )
+    end
+  end
+end