public void GetFileContentIdGood(string id)
        {
            IDBManager fakeDatabase = new FakeDBManager();

            fakeDatabase.AddFileContent(fileContent);
            Assert.AreEqual(fileContent.Id, fakeDatabase.GetFileContentId(id));
        }
        public void GetFileContentIdBadNull(string id)
        {
            IDBManager fakeDatabase = new FakeDBManager();

            Assert.Throws <ArgumentNullException>(() =>
            {
                fakeDatabase.GetFileContentId(id);
            }
                                                  );
        }
        public void GetFileContentIdDoesntExists(string id)
        {
            FakeDBManager fakeDatabase = new FakeDBManager();

            Assert.AreEqual("INVALID", fakeDatabase.GetFileContentId(id));
        }