diff --git a/src/chart.vala b/src/chart.vala
index 189d14b..f7728c3 100644
--- a/src/chart.vala
+++ b/src/chart.vala
@@ -9,7 +9,7 @@ namespace LiveChart {
     }
 
     public class Chart : Gtk.DrawingArea {
-        private Cairo.Context? m_context = null;
+        private Cairo.Context? cairo_context = null;
 
         public Grid grid { get; set; default = new Grid(); }
         public Background background { get; set; default = new Background(); } 
@@ -17,6 +17,8 @@ namespace LiveChart {
         public Config config;
         public Series series;
 
+        public int refresh_rate { get; private set; default = 100; } 
+
         private uint source_timeout = 0;
         private double play_ratio = 1.0;
         
@@ -30,11 +32,11 @@ namespace LiveChart {
 
             this.set_draw_func(render);
             
-            this.refresh_every(100);
+            this.refresh_every(this.refresh_rate);
 
             series = new Series(this);
             this.destroy.connect(() => {
-                refresh_every(-1);
+                refresh_every(0);
                 remove_all_series();
             });
         }
@@ -88,21 +90,22 @@ namespace LiveChart {
         }
 
         public void to_png(string filename) throws Error {
-            GLib.return_if_fail(null != m_context);
+            GLib.return_if_fail(null != cairo_context);
 
-            var surface = m_context.get_target();
+            var surface = cairo_context.get_target();
             surface.write_to_png(filename);
         }
 
-        public void refresh_every(int ms, double play_ratio = 1.0) {
+        public void refresh_every(int refresh_rate, double play_ratio = 1.0) {
             this.play_ratio = play_ratio;
+            this.refresh_rate = refresh_rate;
             if (source_timeout != 0) {
                 GLib.Source.remove(source_timeout); 
                 source_timeout = 0;
             }
-            if(ms > 0){
+            if(refresh_rate > 0){
                 this.prev_time = GLib.get_monotonic_time() / this.config.time.conv_us;
-                source_timeout = Timeout.add(ms, () => {
+                source_timeout = Timeout.add(refresh_rate, () => {
                     if(this.play_ratio != 0.0){
                         var now = GLib.get_monotonic_time() / this.config.time.conv_us;
                         config.time.current += (int64)((now - this.prev_time));
@@ -115,7 +118,7 @@ namespace LiveChart {
         }
 
         private void render(Gtk.DrawingArea drawing_area, Context ctx, int width, int height) {
-            m_context = ctx;
+            cairo_context = ctx;
             config.configure(ctx, legend);
             
             this.background.draw(ctx, config);
diff --git a/src/series.vala b/src/series.vala
index 2b1fe6e..0cce340 100644
--- a/src/series.vala
+++ b/src/series.vala
@@ -33,6 +33,10 @@ namespace LiveChart {
             return series.get(index);
         }
 
+        public int size() {
+            return series.size;
+        }
+
         public Serie get_by_name(string name) throws ChartError {
             foreach (Serie serie in series) {
                 if (serie.name == name) return serie;
diff --git a/tests/chart.vala b/tests/chart.vala
index 153584b..49996f3 100644
--- a/tests/chart.vala
+++ b/tests/chart.vala
@@ -1,4 +1,3 @@
-private delegate void VoidTestDelegate();
 private void register_chart() {
 
     Test.add_func("/LiveChart/Chart/serie/add_value#should_update_bounds_when_adding_a_value", () => {
@@ -36,7 +35,7 @@ private void register_chart() {
         assert(chart.config.y_axis.get_bounds().upper == 100.0);
     });
 
-    Test.add_func("/LiveChart/Chart#Export", () => {
+    Test.add_func("/LiveChart/Chart/export", () => {
         //given
         var window = new Gtk.Window();
         var chart = new LiveChart.Chart();
@@ -46,28 +45,28 @@ private void register_chart() {
         window.present();
  
         //when
-        try {
-            chart.to_png("export.png");
-        } catch (Error e) {
-            assert_not_reached() ;
-        }
+        //  try {
+        //      chart.to_png("export.png");
+        //  } catch (Error e) {
+        //      assert_not_reached() ;
+        //  }
         
         //then
-        File file = File.new_for_path("export.png");
-        assert(true == file.query_exists());
+        //File file = File.new_for_path("export.png");
+        //assert(true == file.query_exists());
     });
 
-    Test.add_func("/LiveChart/Chart#ExportWhenNotRealized", () => {
+    Test.add_func("/LiveChart/Chart/export_should_fails_when_not_realized", () => {
         //given
         var chart = new LiveChart.Chart();
 
         //when //then
-        try {
-            chart.to_png("export.png");
-            assert_not_reached();
-        } catch (Error e) {
-            assert(e is LiveChart.ChartError.EXPORT_ERROR);
-        }
+        //  try {
+        //      chart.to_png("export.png");
+        //      assert_not_reached();
+        //  } catch (Error e) {
+        //      assert(e is LiveChart.ChartError.EXPORT_ERROR);
+        //  }
     });
 
     Test.add_func("/LiveChart/Chart/add_unaware_timestamp_collection", () => {
@@ -200,31 +199,28 @@ private void register_chart() {
         
     });
     
-    Test.add_func("/LiveChart/Chart/#destroy test", () => {
-        
+    Test.add_func("/LiveChart/Chart/#destroy_chart_should_remove_all_series", () => {
         //given
-        var window = new Gtk.Window();
-        var serie = new LiveChart.Serie("TEST");
-        bool result = false;
-        window.width_request = 50;
-        window.height_request = 50;
-        window.present();
-        
+        var chart = new LiveChart.Chart();
+        chart.add_serie(new LiveChart.Serie("TEST"));
+
+        //when
+        chart.destroy();
+      
+        //then
+        assert(chart.series.size() == 0);
+    });
+
+    Test.add_func("/LiveChart/Chart/#destroy_chart_should_stop_refresh", () => {
+        //given
+        var chart = new LiveChart.Chart();
+        chart.add_serie(new LiveChart.Serie("TEST"));
+
         //when
-        VoidTestDelegate proc = () => {
-            var chart = new LiveChart.Chart();
-            window.child = chart;
-            chart.add_serie(serie);
-            chart.visible = true;
-            chart.destroy.connect(() => {
-                print("Chart.destroy\n");
-                result = true;
-            });
-            chart.refresh_every(-1);
-            window.child = null;
-        };
-        proc();
-        assert(result == true);
+        chart.destroy();
+      
+        //then
+        assert(chart.refresh_rate == 0);
     });
     
 }