### Question:
Block { public Instruction last() { if (instructions.isEmpty()) { return null; } return instructions.get(instructions.size() - 1); }  void add(Instruction instruction); void remove(Instruction instruction); Instruction last(); Instruction previous(Instruction instruction);  }### Answer:
@Test void testLast() { var block = new Block(new Label(0, "block")); var instruction = dummyInstruction(); block.add(instruction); assertEquals(instruction, block.last()); }