Tests: Ensure no timers are running at the end of each test (#1920)

This helps fix issues that make tooltip tests sometimes fail when run against
jQuery 3.2 or newer due to timing differences.

Details:
* Add the `moduleAfterEach` function ensuring no timers are running.
* Attach this function via `common.testWidget`.
* Attach this function to most test suites.
* Add a tooltip test helper cleaning up leftover timers.
* Rename legacy `setup`/`teardown` hooks to `beforeEach`/`afterEach`.

Closes gh-1920

2 files changed, 28 insertions, 4 deletions

diff --git a/tests/lib/common.js b/tests/lib/common.js
index 7d3b3db2a..dbb9eea8b 100644
--- a/tests/lib/common.js
+++ b/tests/lib/common.js
@@ -1,7 +1,8 @@
 define( [
 	"qunit",
-	"jquery" ],
-function( QUnit, $ ) {
+	"jquery",
+	"lib/helper"
+], function( QUnit, $, helper ) {
 
 var exports = {};
 
@@ -66,7 +67,7 @@ function testBasicUsage( widget ) {
 }
 
 exports.testWidget = function( widget, settings ) {
-	QUnit.module( widget + ": common widget" );
+	QUnit.module( widget + ": common widget", { afterEach: helper.moduleAfterEach } );
 
 	exports.testJshint( "/widgets/" + widget );
 	testWidgetDefaults( widget, settings.defaults );
diff --git a/tests/lib/helper.js b/tests/lib/helper.js
index 400d85489..2315c5e19 100644
--- a/tests/lib/helper.js
+++ b/tests/lib/helper.js
@@ -2,7 +2,12 @@ define( [
 	"jquery"
 ], function( $ ) {
 
-var exports = {};
+var exports = {},
+
+	// Store the old count so that we only assert on tests that have actually leaked,
+	// instead of asserting every time a test has leaked sometime in the past
+	oldActive = 0,
+	splice = [].splice;
 
 exports.forceScrollableWindow = function( appendTo ) {
 
@@ -28,6 +33,24 @@ exports.onFocus = function( element, onFocus ) {
 	element.on( "focus", fn )[ 0 ].focus();
 };
 
+/**
+ * Ensures that tests have cleaned up properly after themselves. Should be passed as the
+ * afterEach function on all modules' lifecycle object.
+ */
+exports.moduleAfterEach = function( assert ) {
+
+	// Check for (and clean up, if possible) incomplete animations/requests/etc.
+	if ( jQuery.timers && jQuery.timers.length !== 0 ) {
+		assert.equal( jQuery.timers.length, 0, "No timers are still running" );
+		splice.call( jQuery.timers, 0, jQuery.timers.length );
+		jQuery.fx.stop();
+	}
+	if ( jQuery.active !== undefined && jQuery.active !== oldActive ) {
+		assert.equal( jQuery.active, oldActive, "No AJAX requests are still active" );
+		oldActive = jQuery.active;
+	}
+};
+
 return exports;
 
 } );