test.xsd

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:import namespace="http://www.w3.org/XML/1998/namespace"
        schemaLocation="http://www.w3.org/2001/03/xml.xsd"/>
    <xs:element name="tests">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="title"/> 
                <xs:element name="variable" type="Variable" minOccurs="0" maxOccurs="unbounded"/>
                <xs:element name="description"/>
                <xs:element maxOccurs="unbounded" name="test">
                    <xs:complexType>
                        <xs:sequence>
                            <xs:element name="title"/>
                            <xs:element name="variable" type="Variable" minOccurs="0" maxOccurs="unbounded"/>
                            <xs:element name="description"/>
                            <xs:element maxOccurs="unbounded" name="case">
                                <xs:complexType>
                                    <xs:sequence>
                                        <xs:element name="title"/>
                                        <xs:element name="variable" type="Variable" minOccurs="0" maxOccurs="unbounded"/>
                                        <xs:element name="description"/>
                                        <xs:element name="source"/>
                                        <xs:element name="markup"/>
                                        <xs:element name="result"/>
                                    </xs:sequence>
                                </xs:complexType>
                            </xs:element>
                        </xs:sequence>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
            <xs:attribute ref="xml:lang"/>
        </xs:complexType>
    </xs:element>

    <xs:complexType name="Variable">
        <xs:simpleContent>
            <xs:extension base="xs:string">
                <xs:attribute name="name" type="xs:string"/>
            </xs:extension>
        </xs:simpleContent>
    </xs:complexType>

</xs:schema>