drawing_spec.rb

    # passes (from different app)
    it "should associate with a location with location_ids" do
      location = create(:location)
      vendor = create(:vendor, location_ids: [location.id])
      vendor.reload

      vendor.locations.should include(location)
    end

    # fails
    it "should associate with a category with category_ids" do
      category = create(:category)
      drawing = create(:drawing, category_ids: [category.id])
      drawing.reload

      drawing.categories.should include(category)
    end

    # passes
    it "should associate with a category with category_ids" do
      category = create(:category)
      drawing = create(:drawing)
      drawing.category_ids = [category.id]
      drawing.save
      drawing.reload

      drawing.categories.should include(category)
    end

What about drawing.categories(true).should include(category)?

Doesn't help. The reason I went down this trail is selecting categories with a checkbox wasn't working when creating the drawing so I created these tests to help me figure it out. Watching the logs, nothing gets inserted into the db when creating but it does on update. Thanks though!