public void Push_WhenNewElement_ThenAdded()
        {
            // given
            int element = 46;

            // when
            testObject.Push(element);
            // then
            testObject.Should().HaveCount(numbers.Length + 1);
            testObject.GetMin().Should().Be(minimum);
            testObject.GetMax().Should().Be(maximum);
        }
        public void GetMin_WhenEmpty_ThenInvalidOperationException()
        {
            // given
            testObject = new DoubleHeap <int>();
            // when
            Action action = () => testObject.GetMin();

            // then
            action.Should().Throw <InvalidOperationException>();
        }
        public void GetMin_WhenSingleElement_ThenThisElement()
        {
            // given
            int element = 19;

            testObject = new DoubleHeap <int>(new[] { element });
            // when
            int result = testObject.GetMin();

            // then
            result.Should().Be(element);
        }
        public void Push_WhenEmpty_ThenAdded()
        {
            // given
            int element = 19;

            testObject = new DoubleHeap <int>();
            // when
            testObject.Push(element);
            // then
            testObject.Should().HaveCount(1);
            testObject.GetMin().Should().Be(element);
            testObject.GetMax().Should().Be(element);
        }