LogicException: The selected node does not have a form ancestor.

I'm working on fleshing out my functional tests with the integrated PHPUnit functionality added in Laravel 5. I have a form, but its "submit" button is a regular button outside of the form, which onclick event triggers the form to submit. (This is necessary because of layout constraints.)

The error I'm getting is:

LogicException: The selected node does not have a form ancestor.

Here's the relevant unit test:

        $response = $this->actingAs($this->myUser)
            ->visit('testpage')
            ->click('random-link-id')
            ->press('Update Role'); // this is just a regular <button> with an onclick event

Any ideas how to trigger a form submit without pressing a button that has to be within the form tags?