从字符串创建特定数量的字节

I would like to know if there is a way to create a specific number of bytes from a string. I am trying to unit test some part of my code and it can take an array of bytes or a string. But the data that I am getting will consist exactly 132 bytes (where each data point is two byte signed integers that uses 2's complement).I would like to know if there is a way to creat