BibtexLibrary.Tokenizer.Tokenizer.GetPreviousCharacters C# (CSharp) Method

        public string GetPreviousCharacters(int n)
        {
            return _input.Substring(_counter - n, n);
        }

        public void TestPrevious()
        {
            Tokenizer tokenizer = new Tokenizer(new ExpressionDictionary(), @"@book{ aaker:1912,
                                                                                author = { tes~est }
                                                                            }");

            Assert.Throws<ArgumentOutOfRangeException>(() => tokenizer.GetPreviousCharacters(10));

            tokenizer.NextToken();
            tokenizer.NextToken();
            tokenizer.NextToken();
            tokenizer.NextToken();
            tokenizer.NextToken();
            AbstractToken token = tokenizer.NextToken();

            Assert.AreEqual("   author ", tokenizer.GetPreviousCharacters(10));
        }