public void Test_FileExtension()
{
IFilePath filePath = @".\File.txt".ToRelativeFilePath();
Assert.IsTrue(filePath.FileExtension == @".txt");
Assert.IsTrue(filePath.HasExtension(@".txt"));
Assert.IsTrue(filePath.HasExtension(@".TxT"));
Assert.IsTrue(filePath.HasExtension(@".TXT"));
filePath = @"%E%\File.txt".ToEnvVarFilePath();
Assert.IsTrue(filePath.FileExtension == @".txt");
Assert.IsTrue(filePath.HasExtension(@".txt"));
Assert.IsTrue(filePath.HasExtension(@".TxT"));
Assert.IsTrue(filePath.HasExtension(@".TXT"));
filePath = @".\File".ToRelativeFilePath();
Assert.IsTrue(filePath.FileExtension == string.Empty);
filePath = @".\File.".ToRelativeFilePath();
Assert.IsTrue(filePath.FileExtension == string.Empty);
filePath = @"C:\dir1\\//dir2\File.txt.Exe".ToAbsoluteFilePath();
Assert.IsTrue(filePath.FileExtension == @".Exe");
Assert.IsTrue(filePath.HasExtension(@".exe"));
}