diff --git a/tests/unit/accordion/accordion.html b/tests/unit/accordion/accordion.html
index 0a8755fd34..9ea2d36453 100644
--- a/tests/unit/accordion/accordion.html
+++ b/tests/unit/accordion/accordion.html
@@ -9,6 +9,7 @@
 	<script src="../../../external/qunit/qunit.js"></script>
 	<script src="../../../external/jquery-simulate/jquery.simulate.js"></script>
 	<script src="../testsuite.js"></script>
+	<script src="../../../external/qunit-assert-classes/qunit-assert-classes.js"></script>
 	<script>
 	TestHelpers.loadResources({
 		css: [ "core", "accordion" ],
diff --git a/tests/unit/accordion/accordion_common.js b/tests/unit/accordion/accordion_common.js
index 70e04e8475..fb80ef3531 100644
--- a/tests/unit/accordion/accordion_common.js
+++ b/tests/unit/accordion/accordion_common.js
@@ -2,7 +2,11 @@ TestHelpers.commonWidgetTests( "accordion", {
 	defaults: {
 		active: 0,
 		animate: {},
-		classes: {},
+		classes: {
+			"ui-accordion-header": "ui-corner-top",
+			"ui-accordion-header-collapsed": "ui-corner-all",
+			"ui-accordion-content": "ui-corner-bottom"
+		},
 		collapsible: false,
 		disabled: false,
 		event: "click",
diff --git a/tests/unit/accordion/accordion_core.js b/tests/unit/accordion/accordion_core.js
index 721d154875..ea5959e9a2 100644
--- a/tests/unit/accordion/accordion_core.js
+++ b/tests/unit/accordion/accordion_core.js
@@ -6,14 +6,26 @@ var setupTeardown = TestHelpers.accordion.setupTeardown,
 module( "accordion: core", setupTeardown() );
 
 $.each( { div: "#list1", ul: "#navigation", dl: "#accordion-dl" }, function( type, selector ) {
-	test( "markup structure: " + type, function() {
-		expect( 4 );
-		var element = $( selector ).accordion();
-		ok( element.hasClass( "ui-accordion" ), "main element is .ui-accordion" );
-		equal( element.find( ".ui-accordion-header" ).length, 3,
-			".ui-accordion-header elements exist, correct number" );
-		equal( element.find( ".ui-accordion-content" ).length, 3,
-			".ui-accordion-content elements exist, correct number" );
+
+	test( "markup structure: " + type, function( assert ) {
+		expect( 10 );
+		var element = $( selector ).accordion(),
+			headers = element.find( ".ui-accordion-header" ),
+			content = headers.next();
+
+		assert.hasClasses( element, "ui-accordion ui-widget" );
+		equal( headers.length, 3, ".ui-accordion-header elements exist, correct number" );
+		assert.hasClasses( headers[ 0 ],
+			"ui-accordion-header ui-accordion-header-active ui-accordion-icons" );
+		assert.hasClasses( headers[ 1 ],
+			"ui-accordion-header ui-accordion-header-collapsed ui-accordion-icons" );
+		assert.hasClasses( headers[ 2 ],
+			"ui-accordion-header ui-accordion-header-collapsed ui-accordion-icons" );
+		equal( content.length, 3, ".ui-accordion-content elements exist, correct number" );
+		assert.hasClasses( content[ 0 ],
+			"ui-accordion-content ui-widget-content ui-accordion-content-active" );
+		assert.hasClasses( content[ 1 ], "ui-accordion-content ui-widget-content" );
+		assert.hasClasses( content[ 2 ], "ui-accordion-content ui-widget-content" );
 		deepEqual( element.find( ".ui-accordion-header" ).next().get(),
 			element.find( ".ui-accordion-content" ).get(),
 			"content panels come immediately after headers" );
diff --git a/ui/accordion.js b/ui/accordion.js
index 68a4c34ec0..585137841e 100644
--- a/ui/accordion.js
+++ b/ui/accordion.js
@@ -37,6 +37,11 @@ return $.widget( "ui.accordion", {
 	options: {
 		active: 0,
 		animate: {},
+		classes: {
+			"ui-accordion-header": "ui-corner-top",
+			"ui-accordion-header-collapsed": "ui-corner-all",
+			"ui-accordion-content": "ui-corner-bottom"
+		},
 		collapsible: false,
 		event: "click",
 		header: "> li > :first-child,> :not(li):even",
@@ -69,10 +74,10 @@ return $.widget( "ui.accordion", {
 
 	_create: function() {
 		var options = this.options;
+
 		this.prevShow = this.prevHide = $();
-		this.element.addClass( "ui-accordion ui-widget ui-helper-reset" )
-			// ARIA
-			.attr( "role", "tablist" );
+		this._addClass( "ui-accordion", "ui-widget ui-helper-reset" );
+		this.element.attr( "role", "tablist" );
 
 		// don't allow collapsible: false and active: false / null
 		if ( !options.collapsible && (options.active === false || options.active == null) ) {
@@ -95,37 +100,33 @@ return $.widget( "ui.accordion", {
 	},
 
 	_createIcons: function() {
-		var icons = this.options.icons;
+		var icon, children,
+			icons = this.options.icons;
+
 		if ( icons ) {
-			$( "<span>" )
-				.addClass( "ui-accordion-header-icon ui-icon " + icons.header )
-				.prependTo( this.headers );
-			this.active.children( ".ui-accordion-header-icon" )
-				.removeClass( icons.header )
-				.addClass( icons.activeHeader );
-			this.headers.addClass( "ui-accordion-icons" );
+			icon = $( "<span>" );
+			this._addClass( icon, "ui-accordion-header-icon", "ui-icon " + icons.header );
+			icon.prependTo( this.headers );
+			children = this.active.children( ".ui-accordion-header-icon" );
+			this._removeClass( children, icons.header )
+				._addClass( children, null, icons.activeHeader )
+				._addClass( this.headers, "ui-accordion-icons" );
 		}
 	},
 
 	_destroyIcons: function() {
-		this.headers
-			.removeClass( "ui-accordion-icons" )
-			.children( ".ui-accordion-header-icon" )
-				.remove();
+		this._removeClass( this.headers, "ui-accordion-icons" );
+		this.headers.children( ".ui-accordion-header-icon" ).remove();
 	},
 
 	_destroy: function() {
 		var contents;
 
 		// clean up main element
-		this.element
-			.removeClass( "ui-accordion ui-widget ui-helper-reset" )
-			.removeAttr( "role" );
+		this.element.removeAttr( "role" );
 
 		// clean up headers
 		this.headers
-			.removeClass( "ui-accordion-header ui-accordion-header-active ui-state-default " +
-				"ui-corner-all ui-state-active ui-state-disabled ui-corner-top" )
 			.removeAttr( "role" )
 			.removeAttr( "aria-expanded" )
 			.removeAttr( "aria-selected" )
@@ -137,8 +138,6 @@ return $.widget( "ui.accordion", {
 
 		// clean up content panels
 		contents = this.headers.next()
-			.removeClass( "ui-helper-reset ui-widget-content ui-corner-bottom " +
-				"ui-accordion-content ui-accordion-content-active ui-state-disabled" )
 			.css( "display", "" )
 			.removeAttr( "role" )
 			.removeAttr( "aria-hidden" )
@@ -178,14 +177,15 @@ return $.widget( "ui.accordion", {
 			}
 		}
 
-		// #5332 - opacity doesn't cascade to positioned elements in IE
+		// Support: IE8 Only
+		// #5332 / #6059 - opacity doesn't cascade to positioned elements in IE
 		// so we need to add the disabled class to the headers and panels
 		if ( key === "disabled" ) {
-			this.element
-				.toggleClass( "ui-state-disabled", !!value )
-				.attr( "aria-disabled", value );
-			this.headers.add( this.headers.next() )
-				.toggleClass( "ui-state-disabled", !!value );
+			this.element.attr( "aria-disabled", value );
+
+			this._toggleClass( null, "ui-state-disabled", !!value );
+			this._toggleClass( this.headers.add( this.headers.next() ), null, "ui-state-disabled",
+				!!value );
 		}
 	},
 
@@ -270,13 +270,12 @@ return $.widget( "ui.accordion", {
 		var prevHeaders = this.headers,
 			prevPanels = this.panels;
 
-		this.headers = this.element.find( this.options.header )
-			.addClass( "ui-accordion-header ui-state-default ui-corner-all" );
+		this.headers = this.element.find( this.options.header );
+		this._addClass( this.headers, "ui-accordion-header ui-accordion-header-collapsed",
+			"ui-state-default" );
 
-		this.panels = this.headers.next()
-			.addClass( "ui-accordion-content ui-helper-reset ui-widget-content ui-corner-bottom" )
-			.filter( ":not(.ui-accordion-content-active)" )
-			.hide();
+		this.panels = this.headers.next().filter( ":not(.ui-accordion-content-active)" ).hide();
+		this._addClass( this.panels, "ui-accordion-content", "ui-helper-reset ui-widget-content" );
 
 		// Avoid memory leaks (#10056)
 		if ( prevPanels ) {
@@ -291,12 +290,11 @@ return $.widget( "ui.accordion", {
 			heightStyle = options.heightStyle,
 			parent = this.element.parent();
 
-		this.active = this._findActive( options.active )
-			.addClass( "ui-accordion-header-active ui-state-active ui-corner-top" )
-			.removeClass( "ui-corner-all" );
-		this.active.next()
-			.addClass( "ui-accordion-content-active" )
-			.show();
+		this.active = this._findActive( options.active );
+		this._addClass( this.active, "ui-accordion-header-active", "ui-state-active" )
+			._removeClass( this.active, "ui-accordion-header-collapsed" );
+		this._addClass( this.active.next(), "ui-accordion-content-active" );
+		this.active.next().show();
 
 		this.headers
 			.attr( "role", "tab" )
@@ -415,7 +413,8 @@ return $.widget( "ui.accordion", {
 	},
 
 	_eventHandler: function( event ) {
-		var options = this.options,
+		var activeChildren, clickedChildren,
+			options = this.options,
 			active = this.active,
 			clicked = $( event.currentTarget ),
 			clickedIsActive = clicked[ 0 ] === active[ 0 ],
@@ -448,26 +447,23 @@ return $.widget( "ui.accordion", {
 
 		// switch classes
 		// corner classes on the previously active header stay after the animation
-		active.removeClass( "ui-accordion-header-active ui-state-active" );
+		this._removeClass( active, "ui-accordion-header-active", "ui-state-active" );
 		if ( options.icons ) {
-			active.children( ".ui-accordion-header-icon" )
-				.removeClass( options.icons.activeHeader )
-				.addClass( options.icons.header );
+			activeChildren = active.children( ".ui-accordion-header-icon" );
+			this._removeClass( activeChildren, null, options.icons.activeHeader )
+				._addClass( activeChildren, null, options.icons.header );
 		}
 
 		if ( !clickedIsActive ) {
-			clicked
-				.removeClass( "ui-corner-all" )
-				.addClass( "ui-accordion-header-active ui-state-active ui-corner-top" );
+			this._removeClass( clicked, "ui-accordion-header-collapsed" )
+				._addClass( clicked, "ui-accordion-header-active", "ui-state-active" );
 			if ( options.icons ) {
-				clicked.children( ".ui-accordion-header-icon" )
-					.removeClass( options.icons.header )
-					.addClass( options.icons.activeHeader );
+				clickedChildren = clicked.children( ".ui-accordion-header-icon" );
+				this._removeClass( clickedChildren, null, options.icons.header )
+					._addClass( clickedChildren, null, options.icons.activeHeader );
 			}
 
-			clicked
-				.next()
-				.addClass( "ui-accordion-content-active" );
+			this._addClass( clicked.next(), "ui-accordion-content-active" );
 		}
 	},
 
@@ -579,13 +575,12 @@ return $.widget( "ui.accordion", {
 	},
 
 	_toggleComplete: function( data ) {
-		var toHide = data.oldPanel;
+		var toHide = data.oldPanel,
+			prev = toHide.prev();
 
-		toHide
-			.removeClass( "ui-accordion-content-active" )
-			.prev()
-				.removeClass( "ui-corner-top" )
-				.addClass( "ui-corner-all" );
+		this._removeClass( toHide, "ui-accordion-content-active" );
+		this._removeClass( prev, "ui-accordion-header-active" )
+			._addClass( prev, "ui-accordion-header-collapsed" );
 
 		// Work around for rendering bug in IE (#5421)
 		if ( toHide.length ) {