def test_magnitude_of_velocity_is_given_by_pythagoras_theorem(self):
start_position = Position()
end_position = Position(4, 3)
velocity = Velocity(start_position, end_position)
self.assertEquals(5, velocity.magnitude())
def test_angle_of_velocity_is_determined_by_the_arctangent(self):
start_position = Position()
end_posotion = Position(3, 4)
velocity = Velocity(start_position, end_posotion)
self.assertTrue(velocity.angle() > 45)
self.assertTrue(velocity.angle() < 90)
def test_angle_of_velocity_is_45_if_x_and_y_of_end_position_are_the_same(
self):
start_position = Position()
end_position = Position(2, 2)
velocity = Velocity(start_position, end_position)
self.assertEquals(45, velocity.angle())
def test_create_velocity_with_two_positions(self):
start_position = Position()
end_position = Position(4, 3)
velocity = Velocity(start_position, end_position)
self.assertIsNotNone(velocity)
def test_position_changes_when_projectile_is_shoot(self):
initial_position = Position()
projectile = Projectile(Position())
velocity = Velocity(Position(), Position(3, 5))
projectile.shoot(velocity)
self.assertTrue(isinstance(projectile.position()))
self.assertNotEquals(initial_position(), projectile.position())
def test_magnitude_is_zero_if_start_and_end_positions_are_the_same(self):
position = Position(1, 1)
velocity = Velocity(position, position)
self.assertEquals(0, velocity.magnitude())
def test_projectile_shot_with_a_given_angle_follows_a_parabolic_path(self):
projectile = Projectile(Position(0, 3))
velocity = Velocity(Position(0, 3), Position(4, 6))
projectile.shoot(velocity)
self.assertEquals(Position(3, 0), projectile.position())