rerender performance tests

tests/lib/jasmine-ext.js

@@ -211,6 +211,27 @@ beforeEach(function() {
 
 });
 
+
+function spyOnMethod(Class, methodName) {
+	var origMethod = Class.prototype.hasOwnProperty(methodName) ?
+		Class.prototype[methodName] :
+		null;
+
+	var spy = spyOn(Class.prototype, methodName).and.callThrough();
+
+	spy.restore = function() {
+		if (origMethod) {
+			Class.prototype[methodName] = origMethod;
+		}
+		else {
+			delete Class.prototype[methodName];
+		}
+	};
+
+	return spy;
+}
+
+
 // fix bug with jQuery 3 returning 0 height for <td> elements in the IE's
 [ 'height', 'outerHeight' ].forEach(function(methodName) {
 	var orig = $.fn[methodName];

tests/performance/rerenders.js

@@ -0,0 +1,83 @@
+
+describe('rerender performance', function() {
+	var FC = $.fullCalendar;
+
+	pushOptions({
+		defaultDate: '2017-10-04',
+		events: [
+			{ title: 'event 0', start: '2017-10-04' }
+		],
+		windowResizeDelay: 0
+	});
+
+	[
+		{
+			classes: [ 'MonthView', 'DayGrid' ],
+			defaultView: 'month',
+			changeToView: 'list' // does not have DayGrid!
+		},
+		{
+			classes: [ 'AgendaView', 'DayGrid', 'TimeGrid' ],
+			defaultView: 'agendaWeek',
+			changeToView: 'list' // does not have DayGrid!
+		},
+		{
+			classes: [ 'ListView' ],
+			defaultView: 'listWeek',
+			changeToView: 'month'
+		}
+	].forEach(function(settings) {
+		settings.classes.forEach(function(className) {
+			describe('for ' + className + ' in ' + settings.defaultView + ' view', function() {
+				var Class = FC[className];
+
+				it('calls methods a limited number of times', function(done) {
+					var executeDateRender = spyOnMethod(Class, 'executeDateRender');
+					var executeEventRender = spyOnMethod(Class, 'executeEventRender');
+					var updateSize = spyOnMethod(Class, 'updateSize');
+
+					initCalendar({
+						defaultView: settings.defaultView,
+					});
+
+					expect(executeDateRender.calls.count()).toBe(1);
+					expect(executeEventRender.calls.count()).toBe(1);
+					expect(updateSize.calls.count()).toBe(1);
+
+					currentCalendar.changeView(settings.changeToView);
+
+					expect(executeDateRender.calls.count()).toBe(1);
+					expect(executeEventRender.calls.count()).toBe(1);
+					expect(updateSize.calls.count()).toBe(2); // +1
+
+					currentCalendar.changeView(settings.defaultView);
+
+					expect(executeDateRender.calls.count()).toBe(2); // +1
+					expect(executeEventRender.calls.count()).toBe(2); // +1
+					expect(updateSize.calls.count()).toBe(3); // +1
+
+					currentCalendar.rerenderEvents();
+
+					expect(executeDateRender.calls.count()).toBe(2);
+					expect(executeEventRender.calls.count()).toBe(3); // +1
+					expect(updateSize.calls.count()).toBe(5); // +2, TODO: get to just +1
+
+					$(window).trigger('resize');
+
+					setTimeout(function() {
+
+						expect(executeDateRender.calls.count()).toBe(2);
+						expect(executeEventRender.calls.count()).toBe(3);
+						expect(updateSize.calls.count()).toBe(6); // +1
+
+						executeDateRender.restore();
+						executeEventRender.restore();
+						updateSize.restore();
+
+						done();
+					}, 1) // more than windowResizeDelay
+				});
+			});
+		});
+	});
+});