text: import pytest
  from app import PropertyError
  from app.model.bullet import Bullet
  
  
  def test_bullet_velocity(bullet: Bullet) -> None:
      assert bullet.velocity() == 80
  
  
  def test_bullet_axi_x(bullet: Bullet) -> None:
      assert bullet.axi_x == 300
  
  
  def test_bullet_axi_y(bullet: Bullet) -> None:
      assert bullet.axi_y == 300
  
  
  def test_set_bullet_axi_x(bullet: Bullet) -> None:
      bullet.axi_x = 100
      assert bullet.axi_x == 100
  
  
  def test_set_bullet_axi_y(bullet: Bullet) -> None:
      bullet.axi_y = 100
      assert bullet.axi_y == 100
  
  
  def test_set_error_bullet_axi_x(bullet: Bullet) -> None:
      with pytest.raises(PropertyError):
          bullet.axi_x = None
  
  
  def test_set_error_bullet_axi_y(bullet: Bullet) -> None:
      with pytest.raises(PropertyError):
          bullet.axi_y = None
  