add theme-gem feature for bonafide theme gems

this cucumber feature follows the likely steps a theme designer would take
to build a Rubygem of his theme starting from the scaffolding generated by
`jekyll new-theme` command and further checks if the gem built actually
has the files he planned to include.

features/step_definitions.rb

@@ -156,6 +156,31 @@ end
 
 #
 
+When(%r!^I run gem(.*)$!) do |args|
+  run_rubygem(args)
+  if args.include?("--verbose") || ENV["DEBUG"]
+    $stderr.puts "\n#{jekyll_run_output}\n"
+  end
+end
+
+#
+
+When(%r!^I run git add .$!) do
+  run_in_shell("git", "add", ".")
+end
+
+#
+
+When(%r!^I decide to build the theme gem$!) do
+  Dir.chdir(Paths.theme_gem_dir)
+  gemspec = "my-cool-theme.gemspec"
+  File.write(gemspec, File.read(gemspec).sub("TODO: ", ""))
+  File.new("_includes/blank.html", "w")
+  File.new("_sass/blank.scss", "w")
+end
+
+#
+
 When(%r!^I change "(.*)" to contain "(.*)"$!) do |file, text|
   File.open(file, "a") do |f|
     f.write(text)
@@ -179,6 +204,7 @@ Then(%r!^the (.*) directory should +(not )?exist$!) do |dir, negative|
 end
 
 #
+
 Then(%r!^I should (not )?see "(.*)" in "(.*)"$!) do |negative, text, file|
   step %(the "#{file}" file should exist)
   regexp = Regexp.new(text, Regexp::MULTILINE)

features/support/helpers.rb

@@ -8,6 +8,8 @@ class Paths
   SOURCE_DIR = Pathname.new(File.expand_path("../..", __dir__))
   def self.test_dir; source_dir.join("tmp", "jekyll"); end
 
+  def self.theme_gem_dir; source_dir.join("tmp", "jekyll", "my-cool-theme"); end
+
   def self.output_file; test_dir.join("jekyll_output.txt"); end
 
   def self.status_file; test_dir.join("jekyll_status.txt"); end
@@ -88,6 +90,12 @@ end
 
 #
 
+def run_rubygem(args)
+  run_in_shell("gem", *args.strip.split(" "))
+end
+
+#
+
 def run_jekyll(args)
   args = args.strip.split(" ") # Shellwords?
   process = run_in_shell("ruby", Paths.jekyll_bin.to_s, *args, "--trace")

features/theme_gem.feature

@@ -0,0 +1,31 @@
+Feature: Building Theme Gems
+  As a hacker who likes to share my expertise
+  I want to be able to make a bonafide rubygem off my theme
+  In order to share my awesome style skillz with other Jekyllites
+
+  Scenario: Generating a new Jekyll Theme
+    When I run jekyll new-theme my-cool-theme
+    Then I should get a zero exit status
+    And the my-cool-theme directory should exist
+
+  Scenario: Checking if a bonafide Theme gem will be built from generated scaffolding
+    When I run jekyll new-theme my-cool-theme
+    Then I should get a zero exit status
+    And the my-cool-theme directory should exist
+    When I decide to build the theme gem
+    Then I should get a zero exit status
+    When I run git add .
+    Then I should get a zero exit status
+    When I run gem build my-cool-theme.gemspec
+    Then I should get a zero exit status
+    And the "./my-cool-theme-0.1.0.gem" file should exist
+    When I run gem unpack my-cool-theme-0.1.0.gem
+    Then I should get a zero exit status
+    And the my-cool-theme-0.1.0 directory should exist
+    And the "my-cool-theme-0.1.0/_layouts/default.html" file should exist
+    And the "my-cool-theme-0.1.0/_includes/blank.html" file should exist
+    And the "my-cool-theme-0.1.0/_sass/blank.scss" file should exist
+    And the my-cool-theme-0.1.0/.git directory should not exist
+    And the "my-cool-theme-0.1.0/.gitignore" file should not exist
+    And the "my-cool-theme-0.1.0/Gemfile" file should not exist
+    And the "my-cool-theme-0.1.0/my-cool-theme.gemspec" file should not exist