add spec for median

Author: Rustik

spec/features/extensions_spec.rb

@@ -4,7 +4,7 @@
   describe 'string_agg' do
     before { DB.extension :string_agg }
 
-    it 'generates correct sql for Redshift' do      
+    it 'generates correct sql for Redshift' do
       allow(DB).to receive(:adapter_scheme).and_return(:redshift)
       expect(
         DB[:test].
@@ -32,4 +32,32 @@
           )
     end
   end
+
+  describe 'median' do
+    before { DB.extension :median }
+
+    it 'generates correct sql for Redshift' do
+      allow(DB).to receive(:adapter_scheme).and_return(:redshift)
+      expect(
+        DB[:test].
+          select(
+            Sequel.
+              median(:revenue)
+          ).sql).to eq(
+            "SELECT median(\"revenue\") FROM \"test\""
+          )
+    end
+
+    it 'generates correct sql for Postgresql' do
+      allow(DB).to receive(:adapter_scheme).and_return(:postgres)
+      expect(
+        DB[:test].
+          select(
+            Sequel.
+              median(:revenue)
+          ).sql).to eq(
+            "SELECT percentile_disc(0.5) WITHIN GROUP (ORDER BY \"revenue\") FROM \"test\""
+          )
+    end
+  end
 end