class Test

	var _x as int

	get x from var

	def inc
		ensure
			.x == old .x + 1
		body
			_x += 1

	def badInc
		ensure
			.x == old .x
		body
			_x += 1

	def main is shared
		t = Test()
		t.inc
		t.inc
		expect EnsureException
			t.badInc