Question from the C++ test

In C++14, copying instances of the following class

class String
{
    String(std::size_t l)
    : len(l)
    , ptr(std::make_unique<char[]>(l+1))
    {}

public:
    String(char const* s)
    : String(std::strlen(s))
    {
        std::copy_n(s, len + 1, ptr.get());
    }

private:
    std::size_t             len;
    std::unique_ptr<char[]> ptr;
};

void somewhere()
{
    String s1 = "foo";
    String s2 = s1;
}