Test case wikitext:
{{Graph:Chart | width=400 | height=150 | xAxisTitle=X | yAxisTitle=Y | legend=Legend | type=stackedrect | x=1,2,3,4,5,6,7,8 | y1=10,12,6,14,2,10,7,9 | y2=2,4,6,8,13,11,9,2 | y1Title=Data A | y2Title=Data B | colors=seagreen, orchid }}