undefined method `plain_specs' for # (NoMethodError)

Question

I have made a pull of a project that I have in my work and when I tried to run rails db:migrate, the terminal request to install \"Bundler 2\" so I do it.

Answer 1

What is your ruby version? I had same problem.

My ruby version is 2.6.3 and my bundle didn't work in this ruby version. (Bundle is already upgraded to 2.0.2),

So I downgraded my bundle to verion 1.17.3 and it worked.

I with this solution will help you.