Inheritance: extends Stub_Parent_Model, use trait Znck\Eloquent\Traits\BelongsToThrough
 public function test_has_relation()
 {
     $cities_with_country = Stub_Test_Model_City::has('country')->get();
     $all_cities = Stub_Test_Model_City::all();
     $this->assertCount(16, $cities_with_country);
     $this->assertCount(18, $all_cities);
 }
 public function test_custom_foreign_key_through_two()
 {
     $city = Stub_Test_Model_City::where('id', 1)->first();
     $this->assertNotNull($city->offshoreCountry);
     $this->assertEquals(1, $city->offshoreCountry->id);
 }