def test_it_does_an_unconditional_jump(self):
vm = VM()
vm.instructions = [Label('loop'), noop, noop]
vm.pc = 2
Ujmp('loop').execute(vm)
self.assertEqual(vm.pc, 1)
def test_it_does_not_jump_if_non_negative(self):
vm = VM()
vm.instructions = [Label('loop'), noop, noop]
vm.vstack.push(0)
vm.pc = 2
Njmp('loop').execute(vm)
self.assertEqual(len(vm.vstack), 0)
self.assertEqual(vm.pc, 2)
def test_it_jumps_if_zero(self):
vm = VM()
vm.instructions = [Label('loop'), noop, noop]
vm.vstack.push(0)
vm.pc = 2
Zjmp('loop').execute(vm)
self.assertEqual(len(vm.vstack), 0)
self.assertEqual(vm.pc, 1)
def test_it_calls_a_subroutine(self):
vm = VM()
vm.instructions = [noop, Label('f'), noop, noop, noop]
vm.pc = 4
Call('f').execute(vm)
self.assertEqual(len(vm.cstack), 1)
self.assertEqual(vm.cstack.top(), 4)
self.assertEqual(vm.pc, 2)
