Code implementing an isNot(c:Class):Boolean function on the Object prototype

isNotTest.as

package com.newloop.experiments.isnot {

	import asunit.framework.TestCase;

	public class SomeClassATest extends TestCase {
		private var someClassA:SomeClassA;

		public function SomeClassATest(methodName:String=null) {
			super(methodName)
		}

		override protected function setUp():void {
			super.setUp();
			// you only need to do this once, before you objects are created
			Object.prototype.isNot = function(c:Class):Boolean
			{
				return !(this is c);
			}
			someClassA = new SomeClassA();
		}

		override protected function tearDown():void {
			super.tearDown();
			someClassA = null;
		}

		public function testInstantiated():void {
			assertTrue("someClassA is SomeClassA", someClassA is SomeClassA);
		}

		public function testFailure():void {
			assertTrue("Failing test", true);
		}
		
		public function test_isNot_whenIsNot_returns_true():void {
			// requires cast to Object to get round compiler not finding isNot
			var result:Boolean = Object(someClassA).isNot(String);
			assertTrue("IsNot returns true correctly", result);
		}
		
		public function test_isNot_whenIs_returns_false():void {
			// SomeClassA extends SomeClassB
			// requires cast to Object to get round compiler not finding isNot
			var result:Boolean = Object(someClassA).isNot(SomeClassB);
			assertFalse("IsNot returns false correctly", result);
		}
		
	}
}

SomeClassA.as

package com.newloop.experiments.isnot {
	
	public class SomeClassA extends SomeClassB {
		
		public function SomeClassA() {
		} 
	}
}
       

SomeClassB.as

package com.newloop.experiments.isnot {
	
	public class SomeClassB extends Object {
		
		public function SomeClassB() {
		} 
	}
}