NameError: uninitialized constant

I recently opened up pry, ran this:

test =

but got this:

NameError: uninitialized constant TestGem

Not greatly helpful.

It turned out that, despite adding it to my Gemfile and running


I still needed to require the file in pry.

However, the name of the file isn’t obvious if it’s not your own gem. E.g.

require 'guess_incorrect_gem_name'
LoadError: cannot load such file -- guess_incorrect_gem_name

Eventually it seemed to be correct:

require 'guess_gem_name'
=> true

but this didn’t work:

test =
NameError: uninitialized constant GuessGameName

but by looking at the gem file name via:

ls ~/.rvm/gems/ruby-2.1.5/gems/gem_name/lib/gem_name/gemname.rb

I eventually used:

require "gem_name/gemname"

which worked. E.g.

test =
=> #<GemName:0x007fc8aae926c0>

This all seems a lot of guess work.

What I’d like to see (and I’m sure there must be a way of doing this but Google’ing and searching StackOverflow has not turned anything up) is something like this:

gem install gem_name
> # require with 
> require 'gem_name/gemname'
> # use with
> test =