test_divisors = ->
  run_test [

    "divisors(12)",
    "[1,2,3,4,6,12]",

    "divisors(-12)",
    "[1,2,3,4,6,12]",

    "divisors(a)",
    "[1,a]",

    "divisors(-a)",
    "[1,a]",

    "divisors(+3*x+3)",
    "[1,3,1+x,3+3*x]",

    "divisors(+3*x-3)",
    "[1,3,-3+3*x,-1+x]",

    "divisors(-3*x+3)",
    "[1,3,1-x,3-3*x]",

    "divisors(-3*x-3)",
    "[1,3,1+x,3+3*x]",
  ]