gistfile1.cs

 public static MethodInfo GetMethodInfo<T, U>(Expression<Func<T, U>> expression)
        {
            var method = expression.Body as MethodCallExpression;
            if (method != null)
                return method.Method;

            throw new ArgumentException("Expression is wrong");        
        }
        
 public static MethodInfo GetMethodInfo<T, U>(Expression<Action<T>> expression)
        {
            var method = expression.Body as MethodCallExpression;
            if (method != null)
                return method.Method;

            throw new ArgumentException("Expression is wrong");        
        }        


//Then in the route tester you can add

        public bool CompareSignatures(MethodInfo method)
        {
            if (_controllerContext.ControllerDescriptor == null)
                GetControllerType();

            var actionSelector = new ApiControllerActionSelector();
            var x = actionSelector.GetActionMapping(_controllerContext.ControllerDescriptor)[_request.Method.ToString()];

            return x.Any(item => ((MethodBase)(((ReflectedHttpActionDescriptor)item).MethodInfo)).ToString() == ((MethodBase)method).ToString());

        }

//usage

Assert.IsTrue(routeTester.CompareSignatures(ReflectionHelpers.GetMethodInfo((PersonController p) => p.Get())));
Assert.IsTrue(routeTester.CompareSignatures(ReflectionHelpers.GetMethodInfo((PersonController p) => p.Get(new Guid("d39a7401-5ec7-4611-9934-fdcc1be0dc98")))));