public void RelativeDirectory()
        {
            //Arrange
            var relativePath = @"..\folder4\firstproject\file.txt";
            var expected     = @"..\folder4\firstproject";

            //Act
            var actual = ProjectItemExtensions.RelativeDirectory(relativePath);

            //Assert
            Assert.AreEqual(expected, actual);
        }
        public void RelativePath_SameLevel()
        {
            //Arrange
            const string filePath      = @"c:\folder1\folder2\folder3\firstproject\file.txt";
            const string referencePath = @"c:\folder1\folder2\folder3\secondproject\file.txt";
            var          expected      = @"..\firstproject\file.txt";

            //Act
            var actual = ProjectItemExtensions.RelativePath(filePath, referencePath);

            //Assert
            Assert.AreEqual(expected, actual);
        }