add version command and rspec

lib/inferno/apps/cli/main.rb

@@ -4,6 +4,7 @@
 require_relative 'suite'
 require_relative 'suites'
 require_relative 'new'
+require_relative '../../version'
 
 module Inferno
   module CLI
@@ -52,6 +53,11 @@ def suites
       subcommand 'suite', Suite
 
       register(New, 'new', 'new TEST_KIT_NAME', 'Run `inferno new --help` for full help')
+
+      desc 'version', "Output Inferno core version (#{Inferno::VERSION})"
+      def version
+        puts Inferno::VERSION
+      end
     end
   end
 end

lib/inferno/apps/cli/main_spec.rb

@@ -0,0 +1,12 @@
+require 'rspec'
+require 'thor'
+require 'inferno/apps/cli/main'
+require 'inferno/version'
+
+RSpec.describe Inferno::CLI::Main do # rubocop:disable RSpec/FilePath
+  context 'with version command' do
+    it 'outputs current Inferno version' do
+      expect { described_class.new.version }.to output("#{Inferno::VERSION}\n").to_stdout
+    end
+  end
+end