test_denominator = ->
run_test [
"denominator(2/3)",
"3",
"denominator(x)",
"1",
"denominator(1/x)",
"x",
"denominator(a+b)",
"denominator(1/a+1/b)",
"a*b",
# denominator function expands
"denominator(1/(x-1)/(x-2))",
"x^2-3*x+2",
]