}

    def formatTree(Closure cl) {
        withCategories {
            return formatTree(cl.call())
        }
    }

    def withCategories(Closure cl) {
        use(BuildableDOMCategory) {
            return cl.call()
        }
    }

    def format(Node... nodes) {
        format(nodes as List)
    }

    def formatTree(Node... nodes) {
        formatTree(nodes as List)

        _ * classDoc.subClasses >> []

        when:
        def result = parse('<root/>')
        withCategories {
            renderer.mergeContent(classDoc, result)
        }

        then:
        formatTree(result) == '''<root>
    <chapter id="classId">
        <title>Class</title>
        <segmentedlist>
            <segtitle>API Documentation</segtitle>
            <seglistitem>
                <seg>

	"errors"
	"fmt"
	"strconv"
	"strings"
	"unicode/utf8"
)

// A Tree is a tree description, to be signed by a go.sum database server.
type Tree struct {
	N    int64
	Hash Hash
}

// FormatTree formats a tree description for inclusion in a note.
//
// The encoded form is three lines, each ending in a newline (U+000A):
//
//	go.sum database tree
//	N
//	Hash
//

	s.mu.Lock()
	defer s.mu.Unlock()

	size := int64(len(s.records))
	h, err := tlog.TreeHash(size, s.hashes)
	if err != nil {
		return nil, err
	}
	text := tlog.FormatTree(tlog.Tree{N: size, Hash: h})
	signer, err := note.NewSigner(s.signer)
	if err != nil {
		return nil, err
	}
	return note.Sign(&note.Note{Text: string(text)}, signer)
}