Typo fixes [ci skip]

actionpack/test/controller/flash_test.rb

@@ -174,12 +174,12 @@ class FlashTest < ActionController::TestCase
     flash.update(:foo => :foo_indeed, :bar => :bar_indeed)
 
     assert_equal(:foo_indeed, flash.discard(:foo)) # valid key passed
-    assert_nil flash.discard(:unknown) # non existant key passed
+    assert_nil flash.discard(:unknown) # non existent key passed
     assert_equal({:foo => :foo_indeed, :bar => :bar_indeed}, flash.discard().to_hash) # nothing passed
     assert_equal({:foo => :foo_indeed, :bar => :bar_indeed}, flash.discard(nil).to_hash) # nothing passed
 
     assert_equal(:foo_indeed, flash.keep(:foo)) # valid key passed
-    assert_nil flash.keep(:unknown) # non existant key passed
+    assert_nil flash.keep(:unknown) # non existent key passed
     assert_equal({:foo => :foo_indeed, :bar => :bar_indeed}, flash.keep().to_hash) # nothing passed
     assert_equal({:foo => :foo_indeed, :bar => :bar_indeed}, flash.keep(nil).to_hash) # nothing passed
   end

activerecord/lib/active_record/connection_adapters/postgresql/oid.rb

@@ -311,7 +311,7 @@ module ActiveRecord
           h[k] = OID::Identity.new
         }
 
-        # Register an OID type named +name+ with a typcasting object in
+        # Register an OID type named +name+ with a typecasting object in
         # +type+.  +name+ should correspond to the `typname` column in
         # the `pg_type` table.
         def self.register_type(name, type)

activerecord/test/cases/validations_test.rb

@@ -93,7 +93,7 @@ class ValidationsTest < ActiveRecord::TestCase
     assert reply.save(:validate => false)
   end
 
-  def test_validates_acceptance_of_with_non_existant_table
+  def test_validates_acceptance_of_with_non_existent_table
     Object.const_set :IncorporealModel, Class.new(ActiveRecord::Base)
 
     assert_nothing_raised ActiveRecord::StatementInvalid do

activesupport/lib/active_support/core_ext/array/prepend_and_append.rb

@@ -1,7 +1,7 @@
 class Array
-  # The human way of thinking about adding stuff to the end of a list is with append
+  # The human way of thinking about adding stuff to the end of a list is with append.
   alias_method :append,  :<<
 
-  # The human way of thinking about adding stuff to the beginning of a list is with prepend
+  # The human way of thinking about adding stuff to the beginning of a list is with prepend.
   alias_method :prepend, :unshift
 end

railties/test/railties/engine_test.rb

@@ -399,7 +399,7 @@ YAML
       assert $plugin_initializer
     end
 
-    test "midleware referenced in configuration" do
+    test "middleware referenced in configuration" do
       @plugin.write "lib/bukkits.rb", <<-RUBY
         class Bukkits
           def initialize(app)