public void ReturnInput_WhenOnlyOneElement()
        {
            var elements = new int [1];

            var result = OddOccurenceFinder.FindMismatchingElement(elements);

            result.Should().Be(elements[0]);
        }
        public void ReturnMismatchingElement(int[] elements, int expectedResult)
        {
            var result = OddOccurenceFinder.FindMismatchingElement(elements);

            result.Should().Be(expectedResult);
        }