public void DelegatingStream_Flush()
        {
            // Arrange
            Mock<Stream> mockInnerStream = new Mock<Stream>();
            MockDelegatingStream mockStream = new MockDelegatingStream(mockInnerStream.Object);

            // Act
            mockStream.Flush();

            // Assert 
            mockInnerStream.Verify(s => s.Flush(), Times.Once());
        }