public void ConcatTwoTest()
{
int start = 0;
int end = chain.GetLength();
var firstComplexChain = new ComplexChain(chain.Substring(start, end - 1));
var secondComplexChain = new ComplexChain(chain.Substring(end - 1, end));
ComplexChain concatChain = firstComplexChain.Concat(secondComplexChain.ToString());
Assert.True(concatChain.Equals(chain));
}