Mystery Plant

[Oleanda]

There is a plant in a pot in my garden (it was there when I moved in), it is about 2 feet tall and has leaves like a Mahonia aquifolium, except they are not shiny. The plant has not flowered, or even grown much in the two years I been here, it just sits there. I am thinking of planting it in the garden but would like to know what it is first. Any ideas folks?