Add specs for median serializing

app/serializers/analytics_stage_entity.rb

@@ -10,6 +10,7 @@ class AnalyticsStageEntity < Grape::Entity
 
   expose :median, as: :value do |stage|
     # median returns a BatchLoader instance which we first have to unwrap by using to_f
+    # we use to_f to make sure results below 1 are presented to the end-user
     !stage.median.to_f.zero? ? distance_of_time_in_words(stage.median) : nil
   end
 end

spec/serializers/analytics_stage_serializer_spec.rb

@@ -21,4 +21,34 @@ describe AnalyticsStageSerializer do
   it 'contains important elements of AnalyticsStage' do
     expect(subject).to include(:title, :description, :value)
   end
+
+  context 'when median is equal 0' do
+    before do
+      allow_any_instance_of(Gitlab::CycleAnalytics::BaseStage).to receive(:median).and_return(0)
+    end
+
+    it 'value is nil' do
+      expect(subject.fetch(:value)).to be_nil
+    end
+  end
+
+  context 'when median is below 1' do
+    before do
+      allow_any_instance_of(Gitlab::CycleAnalytics::BaseStage).to receive(:median).and_return(0.12)
+    end
+
+    it 'value is equal to median' do
+      expect(subject.fetch(:value)).to eq('less than a minute')
+    end
+  end
+
+  context 'when median is above 1' do
+    before do
+      allow_any_instance_of(Gitlab::CycleAnalytics::BaseStage).to receive(:median).and_return(1.12)
+    end
+
+    it 'value is equal to median' do
+      expect(subject.fetch(:value)).to eq('less than a minute')
+    end
+  end
 end