add helper comments and refactor transport test

Signed-off-by: Jared Quick <jquick@chef.io>

lib/train/platforms/common.rb

@@ -23,6 +23,8 @@ def detect(&block)
         @detect = block
         self
       elsif @detect.nil?
+        # we are returning a block that just returns false here
+        # to skip the family/platform evaluation if detect is not set
         ->(_) { false }
       else
         @detect

lib/train/platforms/detect/scanner.rb

@@ -24,6 +24,8 @@ def scan
       # start with the platform/families who have no families (the top levels)
       top = Train::Platforms.top_platforms
       top.each do |_name, plat|
+        # we are doing a instance_eval here to make sure we have the proper
+        # context with all the detect helper methods
         next unless instance_eval(&plat.detect) == true
 
         # if we have a match start looking at the children

test/unit/helper.rb

@@ -5,4 +5,3 @@
 require 'mocha/setup'
 
 require 'train'
-require 'train/platforms/detect'

test/unit/transports/local_test.rb

@@ -3,18 +3,20 @@
 require 'helper'
 require 'train/transports/local'
 
-$transport = nil
-describe 'local transport' do
-  let(:transport) do
-    if $transport.nil?
-      plat = Train::Platforms.name('mock').in_family('linux')
-      plat.add_platform_methods
-      Train::Platforms::Detect.stubs(:scan).returns(plat)
-      $transport = Train::Transports::Local.new
-    end
+class TransportHelper
+  attr_accessor :transport
 
-    $transport
+  def initialize
+    Train::Platforms::Detect::Specifications::OS.load
+    plat = Train::Platforms.name('mock').in_family('linux')
+    plat.add_platform_methods
+    Train::Platforms::Detect.stubs(:scan).returns(plat)
+    @transport = Train::Transports::Local.new
   end
+end
+
+describe 'local transport' do
+  let(:transport) { TransportHelper.new.transport }
   let(:connection) { transport.connection }
 
   it 'can be instantiated' do
@@ -26,7 +28,7 @@
   end
 
   it 'provides a uri' do
-    connection.uri.must_equal "local://"
+    connection.uri.must_equal 'local://'
   end
 
   it 'doesnt wait to be read' do

test/unit/transports/ssh_test.rb

@@ -4,12 +4,12 @@
 require 'train/transports/ssh'
 
 describe 'ssh transport' do
-  let(:cls) {
+  let(:cls) do
       plat = Train::Platforms.name('mock').in_family('linux')
       plat.add_platform_methods
       Train::Platforms::Detect.stubs(:scan).returns(plat)
       Train::Transports::SSH
-  }
+  end
   let(:conf) {{
     host: rand.to_s,
     password: rand.to_s,