How to put invalid id to get request?

I have issue with testing. I have to check that if user trying to get object which does not exist he must get 404 page.

Here is my route:

Route::get('/posts/{id}', 'PostController@index');

Here is my test:

public function testViewsA404PageWhenPostIsNotFound()
{
    $resp = $this->get('/posts/INVALID_ID');
    $resp->assertStatus(404);
    $resp->assertSee("The page a you looking for could not be found");
}

DB - PostgreSQL

But I get exception:

Illuminate\Database\QueryException: SQLSTATE[22P02]: Invalid text representation

invalid input syntax for integer: "INVALID_ID" (SQL: select * from "posts" where "posts "."id" = INVALID_ID limit 1)

I saw that in one lecture course but they used MySQL as database.