Laravel: Testing POST, model as parameters

I'm using laravel 5.6

I'm trying to launch some tests with phpunit.

I have a store method like the following

public function store(Request $request , CustomModel $custom_model, Task $task )
    {
        $this->validate($request, [  
            'foo' => 'required|max:100',
            'bar' => 'required|in:input,textarea,radio,select',
        ]);

...

So I tried to write the corresponding test, like this

$response = $this->post( route('my.route.name') , [
                            'foo' => '',
                            'bar' => 'input',
                        ]);

But of course as I don't specify the CustomModel and Task, the test fail and tell me

Missing required parameters for [Route: my/route/{custom_model}/name/{task}]

And I don't know how the syntax should be in the test ...

I tried the following

$this->post( route('my.route.name' , ['custom_model' => $model , 'task' => $task]), ['foo' => '', 'bar' => 'input'] )

But I does not seems to work