@Test
public void testGetQuantity() {
assertNull("Quantity", spyStock.getQuantity());
verify(spyStock, times(1)).getQuantity();
}
@Test
public void testSetQuantity() {
spyStock.setQuantity(BigInteger.ZERO);
assertEquals("Quantity", BigInteger.ZERO, spyStock.getQuantity());
verify(spyStock, times(1)).setQuantity(any());
}