class Document
{
    public string FileData { get; set; }
    public string FileRelativePath { get; set; }
}

interface IDocumentRepository
{
    Document Get(int id);
}


abstract class  DocumentFactory
{
    public abstract Document Create(int docId);
}

interface IFileStore
{
    string Read(string fileName);
}

class ConcreteDocumentFactory : DocumentFactory
{
    private IDocumentRepository _db;
    private IFileStore _fileStore;

    public ConcreteDocumentFactory(IDocumentRepository db, IFileStore fileStore)
    {
        _db = db;
        _fileStore = fileStore;
    }

    public override Document Create(int docId)
    {

        Document newDoc = _db.Get(docId);
        newDoc.FileData = _fileStore.Read(newDoc.FileRelativePath);
        return newDoc;
    }
}


/////// Test Code Below

[TestFixture]
class TestClass
{

    class TestFriendlyFileStore : IFileStore
    {
        public string Read(string fileName)
        {

            if (fileName == "sample.txt")
                return "Some File Content";
            throw new Exception("Not good file name.");
        }
    }


    class TestFriendlyDocRepo : IDocumentRepository
    {
        public Document Get(int id)
        {
            if (id != 999)
                return new Document() {FileRelativePath = "sample.txt"};
            throw new Exception("Not good id.");

        }
    }

    [Test]
    public void Test()
    {
        var concreteDocFactory = new ConcreteDocumentFactory(new TestFriendlyDocRepo(), new TestFriendlyFileStore());
        var doc = concreteDocFactory.Create(999);
        Assert.AreEqual(doc.FileData == "Some File Content")

    }
}