def test_it_counts_from_1_to_10(self):
screen = TestScreen()
vm = VM()
vm.screen = screen
vm.instructions = [
Push(1), # Put a 1 on the stack
Label(' '), # Set a Label at this point
Dup(), # Duplicate the top stack item
Putn(), # Output the current value
Push(10), # Put 10 (newline) on the stack...
Putc(), # ...and output the newline
Push(1), # Put a 1 on the stack
Add(), # Increment our current value
Dup(), # Duplicate the value to test it
Push(11), # Push 11 onto the stack
Sub(), # Subtraction
Zjmp('\t'), # If we have a 0, jump to the end
Ujmp(' '), # Jump to the start
Label('\t'), # Set the end label
Discard(), # Discard our accumulator, to be tidy
End() # Finish
]
vm.run()
self.assertEqual(screen.contents, '1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n')
screen.turnOff()
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_find_label(self):
vm = VM()
vm.instructions = [Push(1), Label('a'), Push(2), Label('b'), Add()]
self.assertEqual(vm.find_label('a'), 1)
self.assertEqual(vm.find_label('b'), 3)
with self.assertRaisesRegex(LabelMissingError, 'c'):
vm.find_label('c')
def test_it_executes_each_instruction_one_by_one_until_an_end_instruction_is_reached(
self):
vm = VM()
vm.instructions = [Push(3), Dup(), Mul(), End(), Dup()]
vm.run()
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 9)
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)
def test_it_raises_an_error_when_no_end_instruction_is_reached(self):
vm = VM()
vm.instructions = [Push(3), Dup(), Mul()]
with self.assertRaisesRegex(OutOfBoundsError, 'program counter: 3'):
vm.run()
