Пример простого юнит теста на flexunit:

Код AS3:
package
{
import org.flexunit.asserts.assertEquals;
public class MyCoolModelTest
{
private var model:IMyCoolModel;
[Before]
public function setUp():void
{
model = new MyCoolModel();
}
[After]
public function tearDown():void
{
}
[test]
public function testCountResult():void
{
model.countResult(5, 3);
assertEquals(model.result, 15);
}
}
}

Код AS3:
public class MyCoolModel implements IMyCoolModel
{
private var _result:int;
public function countResult(a:int, b:int):void
{
_result = a * b;
}
public function get result():int
{
return _result;
}
}

Код AS3:
public interface IMyCoolModel
{
function countResult(a:int, b:int):void;
function get result():int;
}