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_retrieves_the_value_from_the_given_address(self):
vm = VM()
vm.memory[1000] = 5
vm.vstack.push(1000)
Retrieve().execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 5)
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_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_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_outputs_the_character_at_the_top_of_the_value_stack(self):
screen = TestScreen()
vm = VM()
vm.screen = screen
vm.vstack.push(97)
Putc().execute(vm)
self.assertEqual(len(vm.vstack), 0)
self.assertEqual(screen.contents, 'a')
screen.turnOff()
def test_it_reads_a_number_and_places_it_at_the_address_on_the_top_of_the_value_stack(
self):
keyboard = TestKeyboard('1234')
vm = VM()
vm.keyboard = keyboard
vm.vstack.push(100)
Getn().execute(vm)
self.assertEqual(len(vm.vstack), 0)
self.assertEqual(vm.memory[100], 1234)
keyboard.detach()
def test_when_divisor_is_zero(self):
vm = VM()
vm.vstack.push(1)
vm.vstack.push(0)
with self.assertRaisesRegex(ZeroDivisionError, 'modulo by zero'):
Mod().execute(vm)
def test_it_pushes_a_number_onto_the_value_stack(self):
vm = VM()
Push(1).execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 1)
def test_it_discards_the_top_item_on_the_value_stack(self):
vm = VM()
vm.vstack.push(1)
Discard().execute(vm)
self.assertEqual(len(vm.vstack), 0)
def test_it_duplicates_the_top_item_on_the_value_stack(self):
vm = VM()
vm.vstack.push(1)
Dup().execute(vm)
self.assertEqual(len(vm.vstack), 2)
self.assertEqual(vm.vstack.pop(), 1)
self.assertEqual(vm.vstack.pop(), 1)
def test_it_adds(self):
vm = VM()
vm.vstack.push(3)
vm.vstack.push(2)
Add().execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 5)
def test_it_mods(self):
vm = VM()
vm.vstack.push(7)
vm.vstack.push(2)
Mod().execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 1)
def test_it_multiplies(self):
vm = VM()
vm.vstack.push(3)
vm.vstack.push(2)
Mul().execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 6)
def test_it_divides(self):
vm = VM()
vm.vstack.push(7)
vm.vstack.push(2)
Div().execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 3)
def test_it_subtracts(self):
vm = VM()
vm.vstack.push(3)
vm.vstack.push(2)
Sub().execute(vm)
self.assertEqual(len(vm.vstack), 1)
self.assertEqual(vm.vstack.top(), 1)
def test_it_stores_the_value_at_the_given_address(self):
vm = VM()
vm.vstack.push(1000)
vm.vstack.push(1)
Store().execute(vm)
self.assertEqual(len(vm.vstack), 0)
self.assertEqual(vm.memory[1000], 1)
def test_it_returns(self):
vm = VM()
vm.cstack.push(5)
self.assertEqual(vm.pc, 0)
Ret().execute(vm)
self.assertEqual(len(vm.cstack), 0)
self.assertEqual(vm.pc, 5)
def test_it_swaps_the_two_top_items_on_the_value_stack(self):
vm = VM()
vm.vstack.push(1)
vm.vstack.push(2)
vm.vstack.push(3)
Swap().execute(vm)
self.assertEqual(len(vm.vstack), 3)
self.assertEqual(vm.vstack.pop(), 2)
self.assertEqual(vm.vstack.pop(), 3)
self.assertEqual(vm.vstack.pop(), 1)
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_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_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()
def test_it_raises_halt(self):
vm = VM()
with self.assertRaises(Halt):
End().execute(vm)
