xing/assert_json — Issue #1: Show the correct line number that breaks the test
Author: alto
Created: 2011-10-27 14:22:12+00:00
State: open

When you have nested assertions like this

```ruby
assert_json @response.body do |json|
json.element "user" do
json.element "name"
end
end
```

and there is no name attribute in the response body, then the line with the name assertion should be shown as the one that breaks, not the top-level line with assert_json.