then:
        doc.classExtensions.size() == 2

        doc.classExtensions[0].pluginId == 'a'
        doc.classExtensions[0].extensionClasses == [n1: extensionA1, n2: extensionA2]
        doc.classExtensions[0].extensionProperties.size() == 2
        doc.classExtensions[0].extensionBlocks.size() == 2

        doc.classExtensions[1].pluginId == 'b'
        doc.classExtensions[1].extensionClasses == [n1: extensionB]

    void addClassBlock(BlockDoc blockDoc) {
        classBlocks.add(blockDoc.forClass(this))
    }

    Collection<ClassExtensionDoc> getClassExtensions() { return classExtensions }

    void addClassExtension(ClassExtensionDoc extensionDoc) {
        classExtensions.add(extensionDoc)
    }

    List<ClassDoc> getSuperTypes() {
        return superClass == null ? interfaces : [superClass] + interfaces
    }

        _ * classDoc.classProperties >> []
        _ * classDoc.classMethods >> []
        _ * classDoc.classBlocks >> []
        _ * classDoc.classExtensions >> []
        _ * classDoc.subClasses >> []

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

        then: