Add tests for read_preference option

Author: comandeo-mongo

Diff for: spec/integration/find_options_spec.rb

@@ -157,4 +157,49 @@
       end
     end
   end
+
+  describe 'read preference' do
+    require_topology :replica_set
+
+    context 'when defined on the client' do
+      let(:client_options) do
+        { read: { mode: :secondary } }
+      end
+
+      let(:collection_options) do
+        {}
+      end
+
+      it 'uses the read preference defined on the client' do
+        collection.find.to_a
+        expect(find_command.command['$readPreference']).to eq('mode' => 'secondary')
+      end
+
+      context 'when defzained on the collection' do
+        let(:collection_options) do
+          { read: { mode: :secondary_preferred } }
+        end
+
+        it 'uses the read concern defined on the collection' do
+          collection.find.to_a
+          expect(find_command.command['$readPreference']).to eq('mode' => 'secondaryPreferred')
+        end
+
+        context 'when defined on the operation' do
+          let(:collection_options) do
+            {}
+          end
+
+          let(:operation_read_concern) do
+            { 'level' => 'available' }
+          end
+
+          it 'uses the read concern defined on the operation' do
+            collection.find({}, read_concern: operation_read_concern).to_a
+            expect(find_command.command['readConcern']).to eq(operation_read_concern)
+          end
+        end
+      end
+    end
+  end
 end