override title from DataFrame if title option is given

Author: ievgrafov

lib/gnuplotrb/plot.rb

@@ -298,7 +298,7 @@ def new_with_options(options)
     end
 
     def set_name_from_daru_dataframe(dataframe)
-      self.title = dataframe.name
+      self.title = dataframe.name unless title
     end
   end
 end

spec/plot_spec.rb

@@ -57,6 +57,14 @@
       it 'takes name for plot from DataFrame' do
         expect(subject.title).to eql(df.name)
       end
+
+      context 'with title option given' do
+        subject { Plot.new(df, title: 'Not a DataFrame') }
+
+        it "uses title option instead of DataFrame name" do
+          expect(subject.title).not_to eql(df.name)
+        end
+      end
     end
   end