Keabsahan akta wasiat yang objeknya telah diikat dengan perjanjian pengikatan jual beli sebelum pewaris meninggal dunia (studi Kasus Putusan Mahkamah Agung Nomor 2855 K/Pdt/2016) = The validity testament deed whose pbject has been bound by sale and purchase agreement begore the tersator dies (case study of decision by the supreme court number 2855 K/Pdt/2016)