Question: This is code of test that is failing:

```
  test "should get index" do
    get products_url
    assert_response :success
  end

```

Error info is ActionView::Template::Error: The asset "MyString" is not present in the asset pipeline.

WTF?

Answer: 
Ran into the same problem but found a simple solution.
First I fixed in /test/fixtures/products.yml

```
one:
  title: MyString
  description: MyText
  image_url: lorem.jpg
  price: 9.99

two:
  title: MyString
  description: MyText
  image_url: lorem.jpg
  price: 9.99

```

Lastly I **actually added into my assets/images an image titled "lorem.jpg"**. I found it confusing since they don't mention this at all on the book but hopefully this little pointer it will get you back on track.
you must make sure images in fixtures exists . [look here](http://intertwingly.net/projects/AWDwR4/checkdepot-226-51/section-8.4.html)