Fix RDoc grammar and ensure hm:t tests can run in isolation. [#1644 state:resolved]

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>

activerecord/lib/active_record/associations.rb

@@ -71,7 +71,7 @@ def initialize(reflection)
 
   # See ActiveRecord::Associations::ClassMethods for documentation.
   module Associations # :nodoc:
-    # These classes will be loaded when associatoins are created.
+    # These classes will be loaded when associations are created.
     # So there is no need to eager load them.
     autoload :AssociationCollection, 'active_record/associations/association_collection'
     autoload :AssociationProxy, 'active_record/associations/association_proxy'

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -23,8 +23,8 @@ def create(attrs = nil)
       end
 
       # Returns the size of the collection by executing a SELECT COUNT(*) query if the collection hasn't been loaded and
-      # calling collection.size if it has. If it's more likely than not that the collection does have a size larger than zero
-      # and you need to fetch that collection afterwards, it'll take one less SELECT query if you use length.
+      # calling collection.size if it has. If it's more likely than not that the collection does have a size larger than zero,
+      # and you need to fetch that collection afterwards, it'll take one fewer SELECT query if you use #length.
       def size
         return @owner.send(:read_attribute, cached_counter_attribute_name) if has_cached_counter?
         return @target.size if loaded?

activerecord/test/cases/associations/has_many_through_associations_test.rb

 require "cases/helper"
 require 'models/post'
 require 'models/person'
+require 'models/reference'
+require 'models/job'
 require 'models/reader'
 require 'models/comment'
 require 'models/tag'