### Question:
HalfArithmetic { public int mul(int... nums) { LOGGER.info("Arithmetic mul {}", VERSION); return oldSource.accumulateMul(nums); } HalfArithmetic(HalfSource newSource, OldSource oldSource); int sum(int... nums); int mul(int... nums); boolean ifHasZero(int... nums);  }### Answer:
@Test public void testMul() { assertEquals(0, arithmetic.mul(-1, 0, 1)); }