public void IstTextFile_ValidFileName_ReturnsTrue(string fileName)
        {
            //Act
            bool result = Stringhelper.IsTextFile(fileName);

            //Assert
            Assert.IsTrue(result);
        }
        public void IsTextFile_InvalidFileName_ReturnsFalse(string fileName)
        {
            bool result = Stringhelper.IsTextFile(fileName);

            Assert.IsFalse(result);
        }