How to simplify composite type in variable

I'm looping through some input and output strings for a unit test, and my first attempt was:

std::vector<std::pair<std::string, std::string>> pairs {{"input1", "output1"}, {"input2", "output2"}};

As you can see it's quite verbose. I've tried to use auto, but g++ complains about the nested init lists.

How can this be simplified?

I realize this might not be the recommended data structure for the job (you could use a std::map for instance) I'm asking this out of pure curiosity.