Despite earning a Tony nomination for Best Play, Colm Toibin's The Testament of Mary will play its final performance on May 5 at Broadway's Walter Kerr Theatre. Starring Fiona Shaw and directed by Deborah Warner, the one-woman show will have played 27 preview and 16 performances at the time of closing. Based on Toibin's novella of the same name, The Testament of Mary tells the unheard story of…