glib/gio/tests/schema-tests/array-default-not-in-choices.gschema.xml

<schemalist>
    <schema id="test">
      <key name="test" type="as">
        <choices>
          <choice value="first" />
          <choice value="last" />
        </choices>
        <default>["first","last","second"]</default>
      </key>
    </schema>
</schemalist>