using Spectre.IO;

public bool CheckSomething()
{
    // Get the full path to "foo/hello.txt" in the current working directory.
    // Note: A path has no knowledge of the actual file. It's just a convenient
    // way to work with file system paths since it does things as normalization
    // automatically.
    var root = new DirectoryPath("foo").MakeAbsolute(_environment);
    var path = root.CombineWithFilePath(new FilePath("hello.txt"));

    // Of course, we could also have done this in one step.
    path = new FilePath("foo/hello.txt").MakeAbsolute(_environment);

    // Now get a file system reference to the file and check if it exist.
    var file = _fileSystem.GetFile(path);
    if (file.Exists)
    {
        // The file exists.
        // Does the file not contain the word "goodbye"?
        var contents = GetFileContents(file);
        if (!contents?.Contains("goodbye") ?? false)
        {
            return true;
        }
    }

    // The file "foo/hello.txt" was not found. Is there a file in any 
    // directory that contains the word "ten" or "tea"?
    // That should return true as well.
    if (_globber.GetFiles("**/*te{n|a}*").Any())
    {
        return true;
    }

    return false;
}

private string GetFileContents(IFile file)
{
    using (var stream = file.OpenRead())
    using (var reader = new StreamReader(stream))
    {
        return reader.ReadToEnd();
    }
}

using Spectre.IO.Testing;

[Fact]
public void Should_Return_False_If_Hello_File_Exists_But_Contains_The_Word_Goodbye()
{
    // Given
    var environment = FakeEnvironment.CreateLinuxEnvironment();
    var filesystem = new FakeFileSystem(environment);
    var globber = new Globber(filesystem, environment);
    var checker = new Checker(filesystem, environment, globber);

    filesystem.CreateFile("foo/bar.txt");
    filesystem.CreateFile("bar/qux.txt");
    filesystem.CreateFile("foo/hello.txt").SetTextContent("Is this goodbye?");

    // When
    var result = checker.CheckSomething();

    // Then
    result.ShouldBeFalse();
}