@Test(expected = ArithmeticException.class)
  // ... due to some kind of number overflow.
  public void
      test_Multiplication_Of_MinSupportingLongValue_And_2_WithExpecting_ArithmeticException() {

    final long arg1 = Long.MIN_VALUE;
    final long arg2 = 2;

    calculatorUnderTest.mul(arg1, arg2);
  }
  @Test
  public void test_Multiplication_Of_Negative_And_Zero_Numbers() {

    final long arg1 = -7;
    final long arg2 = 0;

    long result = calculatorUnderTest.mul(arg1, arg2);

    long expectedResult = 0;
    assertEquals(expectedResult, result);
  }
  @Test
  public void test_Multiplication_Of_Two_Positive_Numbers() {

    final long arg1 = 2;
    final long arg2 = 3;

    long result = calculatorUnderTest.mul(arg1, arg2);

    long expectedResult = 6;
    assertEquals(expectedResult, result);
  }