test_denominator = ->
	run_test [

		"denominator(2/3)",
		"3",

		"denominator(x)",
		"1",

		"denominator(1/x)",
		"x",

		"denominator(a+b)",
		"1",

		"denominator(1/a+1/b)",
		"a*b",

		# denominator function expands

		"denominator(1/(x-1)/(x-2))",
		"x^2-3*x+2",
	]