test_cofactor = ->
  run_test [

    "cofactor([[1,2],[3,4]],1,1)",
    "4",

    "cofactor([[1,2],[3,4]],1,2)",
    "-3",

    "cofactor([[1,2],[3,4]],2,1)",
    "-2",

    "cofactor([[1,2],[3,4]],2,2)",
    "1",

    "cofactor([[1,2,3],[4,5,6],[7,8,9]],1,2)",
    "6",
  ]