ActionController::UrlGenerationError, No route matches

I've read through every similar question I could find and still can't figure out my problem.

# routes.rb
Rails.application.routes.draw do
  resources :lists, only: [:index, :show, :create, :update, :destroy] do
    resources :items, except: [:new]
  end
end

---

# items_controller.rb (excerpt)
class ItemsController < ApplicationController
  ...

  def create
    @list = List.find(params[:list_id])
    ...
  end
  ...
end

---

# items_controller_spec.rb (excerpt)
RSpec.describe ItemsController, type: :controller do
   ...

  let!(:list) { List.create(title: "New List title") }

  let(:valid_item_attributes) {
    { title: "Some Item Title", complete: false, list_id: list.id }
  }

  let!(:item) { list.items.create(valid_item_attributes) }
  describe "POST #create" do
    context "with valid params" do
      it "creates a new item" do
        expect {
          post :create, { item: valid_item_attributes, format: :json  }
        }.to change(Item, :count).by(1)
      end
    end
  end
  ...
end

And the RSpec error:

1) ItemsController POST #create with valid params creates a new item
     Failure/Error: post :create, { item: valid_item_attributes, format: :json  }
     ActionController::UrlGenerationError:
       No route matches {:action=>"create", :controller=>"items", :format=>:json, :item=>{:title=>"Some Item Title", :complete=>false, :list_id=>1}}

The output from rake routes:

list_items     GET    /lists/:list_id/items(.:format)          items#index
               POST   /lists/:list_id/items(.:format)          items#create
edit_list_item GET    /lists/:list_id/items/:id/edit(.:format) items#edit
     list_item GET    /lists/:list_id/items/:id(.:format)      items#show
               PATCH  /lists/:list_id/items/:id(.:format)      items#update
               PUT    /lists/:list_id/items/:id(.:format)      items#update
               DELETE /lists/:list_id/items/:id(.:format)      items#destroy

I can successfully create a new item in an existing list via curl which tells me that the route is ok, I must be doing something wrong in my test.

curl -i -X POST -H "Content-Type:application/json" -H "X-User-Email:admin@example.com" -H "X-Auth-xxx" -d '{ "item": { "title": "new item", "complete": "false"} }' http://localhost:3000/lists/5/items

I am really confused. My routes are setup correctly. A ItemsController#create method definitely exists. The rest of the tests in items_controller_spec.rb pass without issue.

Am I missing something obvious?

Here are the fixes I had to make to my tests (items_controller_spec.rb). I was not passing the correct hash to post create:.

  describe "POST #create" do
    context "with valid params" do
      it "creates a new item" do
        expect {
          post :create, { list_id: list.id, item: valid_item_attributes, format: :json  }
        }.to change(Item, :count).by(1)
      end

      it "assigns a newly created item as @item" do
        post :create, { list_id: list.id, item: valid_item_attributes, format: :json  }

        expect(assigns(:item)).to be_a(Item)
        expect(assigns(:item)).to be_persisted
      end
    end # "with valid params"

    context "with invalid params" do
      it "assigns a newly created but unsaved item as @item" do
        post :create, { list_id: list.id, item: invalid_item_attributes, format: :json  }

        expect(assigns(:item)).to be_a_new(Item)
      end

      it "returns unprocessable_entity status" do
        put :create, { list_id: list.id, item: invalid_item_attributes, format: :json }

        expect(response.status).to eq(422)
      end
    end # "with invalid params"
  end # "POST #create"