the assertions are the wrong way around:

```ruby
assert_equal expected, actual
```

which makes:

```ruby
assert_equal "uninitialized constant #{default_class_name}", e.message
assert_equal default_class_name, e.name
```

looking at that, I think it's better to inline `default_class_name` as well. it just reads much better:

```ruby
assert_equal "uninitialized constant ActiveRecord::Base::NonexistentModel", e.message
assert_equal "ActiveRecord::Base::NonexistentModel", e.name
```