methodnotallowedhttpexception in routecollection.php line 218

I know this is duplicate problem. Still I'm not able to correct this problem so can anyone help?

Routes.php

   Route::post('/form-submit',[
   'uses' => 'UserController@formSubmit',
   'as' => 'f.submit',
]);

UserController.php

public function formSubmit() #form-submit
{
   echo"Form Submit Method";
}

test_view.php

@extends('Layout.master')
@section('Content')
 {!! Form::open([
         'route' => 'f.submit', 'method' => 'post'
 ]) !!}
  {!! Form::test('username') !!}
  {!! Form::submit('submit')!!}
 {!! Form::close() !!}
@endsection

If I'm using get method for this code. then directly it is showing Form Submit Method and if I'm using post method then it is showing above error

via Giridhari Lal