Are gems folder specific?

I have an old Ruby on Rails project that I work on as a hobby, but I have never implemented Rspec testing.

Now I would like to do so, so I am reading the fine book 'Effective Testing with Rspec 3'. I would assume the techniques used in the Rspec book and the rspec gem are applicable to the rspec-rails gem, because I got the rspec book from rspec.info, which only offers documentation for rspec-rails and its dependencies. I assume rspec-rails auto-creates the sub folders and files in a RoR project etc. Which one I'm going to use to implement the tests I'm not sure at this point.

Anyway I apparently have rspec installed in my old hobby PROJECT directory (rspec -v from the project directory)

3.5.4

and rspec-rails is also a gem inside the project Gemfile (an outdated version, but current to the time of writing the book), which is also installed along with rspec, according to gem list --local, but I also get 'command not found' with rspec-rails -v from within the old project directory.

So I have created a new folder called rspectest, in which I will use to implement the examples and instructions in the book. However, following the instructions in Chapter 1:

$ gem install rspec -v 3.6.0
Successfully installed rspec-support-3.6.0
Successfully installed rspec-core-3.6.0
Successfully installed diff-lcs-1.3
Successfully installed rspec-expectations-3.6.0
Successfully installed rspec-mocks-3.6.0
Successfully installed rspec-3.6.0
6 gems installed

I have attempted to similarily install rspec in my new rspectest folder, but I get error:

ERROR:  Could not find a valid gem 'rspec' (= 3.5.4) in any repository
ERROR:  Possible alternatives: r_spec

The reason I ask is because on page 7 it asks to run the command rspec from the project directory, to see the results of an example, and I get:

Command 'rspec' not found, but can be installed with:

sudo apt install ruby-rspec-core

So I have to assume this command will allow access to the gem from this particular new rspec testing folder only, if typed from within the directory (?):

sudo apt install ruby-rspec-core

And will not mess with the gems of different project folders, which I assume is the point of gemfile etc, in case different versions of gems are installed locally.

... guess I about figured that one out, my apologies. I'll delete this unless the above command doesn't work. EDIT: pending answers to these questions:

1. Are all folders independent of each other, generally, as far as gems and their accessibility?

2. Do I need bundle to install a gem in a particular folder? I assume not since gem install is a thing, and would require setting up a Rails project, which I could do, but it's literally example #1 in the book.

3. If I go sudo apt install ruby-rspec-core in a random folder (and it installs another version or something weird), is that going to affect my old project folder?

I also assume not, but it'd be nice to clarify why the book examples aren't working off the bat. I dislike having to reinstall the repo or having to wipe the drive when i start experimenting, especially when it's only on page 4

So your question is a bit confusing but I'll just give you a general overview of how gems are managed on your machine.

Typically in a rails project there is a Gemfile that defines your ruby version as well as the gems you need for your projects. Sometimes they will have specific version specified as well 'gem 'aws-ses-v4', '~> 0.8.1'

Also it is good practice to use something like either rvm or rbenv(my preference) to handle ruby management. This is useful for having multiple versions of ruby on your computer. For rbenv you will have a .ruby-version file that you use to set the ruby version and anytime you are in that project directory and run a command rbenv will check that file to determine which ruby version its using and where it should look to find gems, etc.

Now if you aren't using that you are going to need to manually set what version of ruby you are using in terminal and what I'm suspecting you have happening is that you have multiple ruby versions and one of which has rspec installed while the other doesn't.

You should never really need to manually run gem install besides for bundler, and then use a Gemfile and bundle install for everything else.

If you are manually running the gem install command its going to drop the gem inside of the your local directory for the ruby version you are currently using. This will be different based of what kind of computer you are using. For me using rbenv its ~/.rbenv/versions/2.3.8/lib/ruby/gems/2.3.0/gems but not overly sure where it is by default.