Add simple spec for build script

spec/build_spec.rb

@@ -0,0 +1,8 @@
+$plugin_path = File.expand_path('../..', __FILE__)
+
+describe 'build script' do
+  it 'should run and return success code' do
+    Dir.chdir($plugin_path)
+    system('./build')
+  end
+end

spec/loading_spec.rb

@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe "My Vim plugin" do
-  languages = Dir["#{PLUGIN_PATH}/syntax/*.vim"].map { |f| f.split('/').last.gsub('.vim', '') }
+  languages = Dir["#{$plugin_path}/syntax/*.vim"].map { |f| f.split('/').last.gsub('.vim', '') }
 
   languages.each do |lang|
     it "should parse .#{lang} file" do

spec/spec_helper.rb

@@ -1,8 +1,7 @@
 require 'vimrunner'
 require 'vimrunner/rspec'
 
-PLUGIN_PATH = File.expand_path('../..', __FILE__)
-puts PLUGIN_PATH
+$plugin_path = File.expand_path('../..', __FILE__)
 
 Vimrunner::RSpec.configure do |config|
   # Use a single Vim instance for the test suite. Set to false to use an
@@ -15,7 +14,7 @@ Vimrunner::RSpec.configure do |config|
     vim = Vimrunner.start
 
     # Setup your plugin in the Vim instance
-    vim.add_plugin(PLUGIN_PATH)
+    vim.add_plugin($plugin_path)
 
     # The returned value is the Client available in the tests.
     vim