@spec document_for(module(), atom(), non_neg_integer(), Keyword.t()) :: String.t()

Returns a document containing the fields in a type and any sub-types down to a limited depth of nesting (default 3).

This is helpful for generating a document to use for testing your GraphQL API. This function will always return all fields in the given type, ensuring that there aren't any accidental fields with resolver functions that aren't tested in at least some fashion.

Example

iex> document_for(:user, 2)

```
name
age
posts {
  title
  subtitle
}
comments {
  body
}
```

@spec fields_for(module(), atom(), non_neg_integer()) :: [fields] | atom()
when fields: atom() | {atom(), [fields]}

Returns all fields in a type and any sub-types down to a limited depth of nesting (default 3).

This is helpful for converting a struct or map into an expected response that is a bare map and which can be used in some of the other assertions below.