diff --git a/addons/point_of_sale/static/src/js/screens.js b/addons/point_of_sale/static/src/js/screens.js
index fc9649129ab..48dbfd28b90 100644
--- a/addons/point_of_sale/static/src/js/screens.js
+++ b/addons/point_of_sale/static/src/js/screens.js
@@ -1945,12 +1945,7 @@ var PaymentScreenWidget = ScreenWidget.extend({
         }
 
         var lines = order.get_paymentlines();
-        var due   = order.get_due();
-        var extradue = 0;
-        if (due && lines.length  && due !== order.get_due(lines[lines.length-1])) {
-            extradue = due;
-        }
-
+        var extradue = this.compute_extradue(order);
 
         this.$('.paymentlines-container').empty();
         var lines = $(QWeb.render('PaymentScreen-Paymentlines', { 
@@ -1970,6 +1965,14 @@ var PaymentScreenWidget = ScreenWidget.extend({
             
         lines.appendTo(this.$('.paymentlines-container'));
     },
+    compute_extradue: function (order) {
+        var lines = order.get_paymentlines();
+        var due   = order.get_due();
+        if (due && lines.length  && due !== order.get_due(lines[lines.length-1])) {
+            return due;
+        }
+        return 0;
+    },
     click_paymentmethods: function(id) {
         var payment_method = this.pos.payment_methods_by_id[id]
         this.pos.get_order().add_paymentline(payment_method);
diff --git a/addons/point_of_sale/views/pos_session_view.xml b/addons/point_of_sale/views/pos_session_view.xml
index 2ef12e16b2e..afc0cab74d6 100644
--- a/addons/point_of_sale/views/pos_session_view.xml
+++ b/addons/point_of_sale/views/pos_session_view.xml
@@ -13,13 +13,13 @@
                         attrs="{'invisible' : ['|', ('cash_control', '=', False), ('state', '!=', 'opening_control')]}" class="oe_highlight"/>
                     <button name="open_frontend_cb" type="object" string="Continue Selling" states="opened"
                         class="oe_highlight"/>
-                    <button name="action_pos_session_closing_control" type="object" string="End of Session"
+                    <button id="end_session_opened" name="action_pos_session_closing_control" type="object" string="End of Session"
                         attrs="{'invisible' : ['|', ('cash_control', '=', False),('state', '!=', 'opened')]}"
                         class="oe_highlight"/>
-                    <button name="action_pos_session_closing_control" type="object" string="Validate Closing &amp; Post Entries"
+                    <button id="validate_opened" name="action_pos_session_closing_control" type="object" string="Validate Closing &amp; Post Entries"
                         attrs="{'invisible' : ['|', ('cash_control', '=', True),('state', '!=', 'opened')]}"
                         class="oe_highlight"/>
-                    <button name="action_pos_session_validate" type="object" string="Validate Closing &amp; Post Entries" states="closing_control"
+                    <button id="validate_closing_control" name="action_pos_session_validate" type="object" string="Validate Closing &amp; Post Entries" states="closing_control"
                         class="oe_highlight"/>
 
                     <field name="state" widget="statusbar" statusbar_visible="new_session,opening_control,opened,closing_control,closed" nolabel="1" />