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+# :title: Transaction::Simple
+#
+# == Licence
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to
+# deal in the Software without restriction, including without limitation the
+# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+# sell copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+# IN THE SOFTWARE.
+#--
+# Transaction::Simple
+#   Simple object transaction support for Ruby
+#   Version 1.11
+#
+# Copyright (c) 2003 Austin Ziegler
+#
+# $Id: simple.rb,v 1.2 2004/08/20 13:56:37 webster132 Exp $
+#
+# ==========================================================================
+# Revision History ::
+# YYYY.MM.DD  Change ID   Developer
+#             Description
+# --------------------------------------------------------------------------
+# 2003.07.29              Austin Ziegler
+#             Added debugging capabilities and VERSION string.
+# 2003.08.21              Austin Ziegler
+#             Added named transactions.
+#
+# ==========================================================================
+#++
+require 'thread'
+
+  # The "Transaction" namespace can be used for additional transactional
+  # support objects and modules.
+module Transaction
+
+    # A standard exception for transactional errors.
+  class TransactionError < StandardError; end
+    # A standard exception for transactional errors involving the acquisition
+    # of locks for Transaction::Simple::ThreadSafe.
+  class TransactionThreadError < StandardError; end
+
+    # = Transaction::Simple for Ruby
+    # Simple object transaction support for Ruby
+    #
+    # == Introduction
+    #
+    # Transaction::Simple provides a generic way to add active transactional
+    # support to objects. The transaction methods added by this module will
+    # work with most objects, excluding those that cannot be <i>Marshal</i>ed
+    # (bindings, procedure objects, IO instances, or singleton objects).
+    #
+    # The transactions supported by Transaction::Simple are not backed
+    # transactions; that is, they have nothing to do with any sort of data
+    # store. They are "live" transactions occurring in memory and in the
+    # object itself. This is to allow "test" changes to be made to an object
+    # before making the changes permanent.
+    #
+    # Transaction::Simple can handle an "infinite" number of transactional
+    # levels (limited only by memory). If I open two transactions, commit the
+    # first, but abort the second, the object will revert to the original
+    # version.
+    # 
+    # Transaction::Simple supports "named" transactions, so that multiple
+    # levels of transactions can be committed, aborted, or rewound by
+    # referring to the appropriate name of the transaction. Names may be any
+    # object *except* +nil+.
+    #
+    # Copyright::   Copyright © 2003 by Austin Ziegler
+    # Version::     1.1
+    # Licence::     MIT-Style
+    #
+    # Thanks to David Black for help with the initial concept that led to this
+    # library.
+    #
+    # == Usage
+    #   include 'transaction/simple'
+    #
+    #   v = "Hello, you."               # => "Hello, you."
+    #   v.extend(Transaction::Simple)   # => "Hello, you."
+    #
+    #   v.start_transaction             # => ... (a Marshal string)
+    #   v.transaction_open?             # => true
+    #   v.gsub!(/you/, "world")         # => "Hello, world."
+    #
+    #   v.rewind_transaction            # => "Hello, you."
+    #   v.transaction_open?             # => true
+    #
+    #   v.gsub!(/you/, "HAL")           # => "Hello, HAL."
+    #   v.abort_transaction             # => "Hello, you."
+    #   v.transaction_open?             # => false
+    #
+    #   v.start_transaction             # => ... (a Marshal string)
+    #   v.start_transaction             # => ... (a Marshal string)
+    #
+    #   v.transaction_open?             # => true
+    #   v.gsub!(/you/, "HAL")           # => "Hello, HAL."
+    #
+    #   v.commit_transaction            # => "Hello, HAL."
+    #   v.transaction_open?             # => true
+    #   v.abort_transaction             # => "Hello, you."
+    #   v.transaction_open?             # => false
+    #
+    # == Named Transaction Usage
+    #   v = "Hello, you."               # => "Hello, you."
+    #   v.extend(Transaction::Simple)   # => "Hello, you."
+    #   
+    #   v.start_transaction(:first)     # => ... (a Marshal string)
+    #   v.transaction_open?             # => true
+    #   v.transaction_open?(:first)     # => true
+    #   v.transaction_open?(:second)    # => false
+    #   v.gsub!(/you/, "world")         # => "Hello, world."
+    #   
+    #   v.start_transaction(:second)    # => ... (a Marshal string)
+    #   v.gsub!(/world/, "HAL")         # => "Hello, HAL."
+    #   v.rewind_transaction(:first)    # => "Hello, you."
+    #   v.transaction_open?             # => true
+    #   v.transaction_open?(:first)     # => true
+    #   v.transaction_open?(:second)    # => false
+    #   
+    #   v.gsub!(/you/, "world")         # => "Hello, world."
+    #   v.start_transaction(:second)    # => ... (a Marshal string)
+    #   v.gsub!(/world/, "HAL")         # => "Hello, HAL."
+    #   v.transaction_name              # => :second
+    #   v.abort_transaction(:first)     # => "Hello, you."
+    #   v.transaction_open?             # => false
+    #   
+    #   v.start_transaction(:first)     # => ... (a Marshal string)
+    #   v.gsub!(/you/, "world")         # => "Hello, world."
+    #   v.start_transaction(:second)    # => ... (a Marshal string)
+    #   v.gsub!(/world/, "HAL")         # => "Hello, HAL."
+    #   
+    #   v.commit_transaction(:first)    # => "Hello, HAL."
+    #   v.transaction_open?             # => false
+    #
+    # == Contraindications
+    #
+    # While Transaction::Simple is very useful, it has some severe limitations
+    # that must be understood. Transaction::Simple:
+    #
+    # * uses Marshal. Thus, any object which cannot be <i>Marshal</i>ed cannot
+    #   use Transaction::Simple.
+    # * does not manage resources. Resources external to the object and its
+    #   instance variables are not managed at all. However, all instance
+    #   variables and objects "belonging" to those instance variables are
+    #   managed. If there are object reference counts to be handled,
+    #   Transaction::Simple will probably cause problems.
+    # * is not inherently thread-safe. In the ACID ("atomic, consistent,
+    #   isolated, durable") test, Transaction::Simple provides CD, but it is
+    #   up to the user of Transaction::Simple to provide isolation and
+    #   atomicity. Transactions should be considered "critical sections" in
+    #   multi-threaded applications. If thread safety and atomicity is
+    #   absolutely required, use Transaction::Simple::ThreadSafe, which uses a
+    #   Mutex object to synchronize the accesses on the object during the
+    #   transactional operations.
+    # * does not necessarily maintain Object#__id__ values on rewind or abort.
+    #   This may change for future versions that will be Ruby 1.8 or better
+    #   *only*. Certain objects that support #replace will maintain
+    #   Object#__id__.
+    # * Can be a memory hog if you use many levels of transactions on many
+    #   objects.
+    #
+  module Simple
+    VERSION = '1.1.1.0';
+
+      # Sets the Transaction::Simple debug object. It must respond to #<<.
+      # Sets the transaction debug object. Debugging will be performed
+      # automatically if there's a debug object. The generic transaction error
+      # class.
+    def self.debug_io=(io)
+      raise TransactionError, "Transaction Error: the transaction debug object must respond to #<<" unless io.respond_to?(:<<)
+      @tdi = io
+    end
+
+      # Returns the Transaction::Simple debug object. It must respond to #<<.
+    def self.debug_io
+      @tdi
+    end
+
+      # If +name+ is +nil+ (default), then returns +true+ if there is
+      # currently a transaction open.
+      #
+      # If +name+ is specified, then returns +true+ if there is currently a
+      # transaction that responds to +name+ open.
+    def transaction_open?(name = nil)
+      if name.nil?
+        Transaction::Simple.debug_io << "Transaction [#{(@__transaction_checkpoint__.nil?) ? 'closed' : 'open'}]\n" unless Transaction::Simple.debug_io.nil?
+        return (not @__transaction_checkpoint__.nil?)
+      else
+        Transaction::Simple.debug_io << "Transaction(#{name.inspect}) [#{(@__transaction_checkpoint__.nil?) ? 'closed' : 'open'}]\n" unless Transaction::Simple.debug_io.nil?
+        return ((not @__transaction_checkpoint__.nil?) and @__transaction_names__.include?(name))
+      end
+    end
+
+      # Returns the current name of the transaction. Transactions not
+      # explicitly named are named +nil+.
+    def transaction_name
+      raise TransactionError, "Transaction Error: No transaction open." if @__transaction_checkpoint__.nil?
+      Transaction::Simple.debug_io << "#{'|' * @__transaction_level__} Transaction Name: #{@__transaction_names__[-1].inspect}\n" unless Transaction::Simple.debug_io.nil?
+      @__transaction_names__[-1]
+    end
+
+      # Starts a transaction. Stores the current object state. If a
+      # transaction name is specified, the transaction will be named.
+      # Transaction names must be unique. Transaction names of +nil+ will be
+      # treated as unnamed transactions.
+    def start_transaction(name = nil)
+      @__transaction_level__ ||= 0
+      @__transaction_names__ ||= []
+
+      if name.nil?
+        @__transaction_names__ << nil
+        s = ""
+      else
+        raise TransactionError, "Transaction Error: Named transactions must be unique." if @__transaction_names__.include?(name)
+        @__transaction_names__ << name
+        s = "(#{name.inspect})"
+      end
+
+      @__transaction_level__ += 1
+
+      Transaction::Simple.debug_io << "#{'>' * @__transaction_level__} Start Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+
+      @__transaction_checkpoint__ = Marshal.dump(self)
+    end
+
+      # Rewinds the transaction. If +name+ is specified, then the intervening
+      # transactions will be aborted and the named transaction will be
+      # rewound. Otherwise, only the current transaction is rewound.
+    def rewind_transaction(name = nil)
+      raise TransactionError, "Transaction Error: Cannot rewind. There is no current transaction." if @__transaction_checkpoint__.nil?
+      if name.nil?
+        __rewind_this_transaction
+        s = ""
+      else
+        raise TransactionError, "Transaction Error: Cannot rewind to transaction #{name.inspect} because it does not exist." unless @__transaction_names__.include?(name)
+        s = "(#{name})"
+
+        while @__transaction_names__[-1] != name
+          @__transaction_checkpoint__ = __rewind_this_transaction
+          Transaction::Simple.debug_io << "#{'|' * @__transaction_level__} Rewind Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+          @__transaction_level__ -= 1
+          @__transaction_names__.pop
+        end
+        __rewind_this_transaction
+      end
+      Transaction::Simple.debug_io << "#{'|' * @__transaction_level__} Rewind Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+      self
+    end
+
+      # Aborts the transaction. Resets the object state to what it was before
+      # the transaction was started and closes the transaction. If +name+ is
+      # specified, then the intervening transactions and the named transaction
+      # will be aborted. Otherwise, only the current transaction is aborted.
+    def abort_transaction(name = nil)
+      raise TransactionError, "Transaction Error: Cannot abort. There is no current transaction." if @__transaction_checkpoint__.nil?
+      if name.nil?
+        __abort_transaction(name)
+      else
+        raise TransactionError, "Transaction Error: Cannot abort nonexistant transaction #{name.inspect}." unless @__transaction_names__.include?(name)
+
+        __abort_transaction(name) while @__transaction_names__.include?(name)
+      end
+      self
+    end
+
+      # If +name+ is +nil+ (default), the current transaction level is closed
+      # out and the changes are committed.
+      #
+      # If +name+ is specified and +name+ is in the list of named
+      # transactions, then all transactions are closed and committed until the
+      # named transaction is reached.
+    def commit_transaction(name = nil)
+      raise TransactionError, "Transaction Error: Cannot commit. There is no current transaction." if @__transaction_checkpoint__.nil?
+
+      if name.nil?
+        s = ""
+        __commit_transaction
+        Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} Commit Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+      else
+        raise TransactionError, "Transaction Error: Cannot commit nonexistant transaction #{name.inspect}." unless @__transaction_names__.include?(name)
+        s = "(#{name})"
+
+        while @__transaction_names__[-1] != name
+          Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} Commit Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+          __commit_transaction
+        end
+        Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} Commit Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+        __commit_transaction
+      end
+      self
+    end
+
+      # Alternative method for calling the transaction methods. An optional
+      # name can be specified for named transaction support.
+      #
+      # #transaction(:start)::  #start_transaction
+      # #transaction(:rewind):: #rewind_transaction
+      # #transaction(:abort)::  #abort_transaction
+      # #transaction(:commit):: #commit_transaction
+      # #transaction(:name)::   #transaction_name
+      # #transaction::          #transaction_open?
+    def transaction(action = nil, name = nil)
+      case action
+      when :start
+        start_transaction(name)
+      when :rewind
+        rewind_transaction(name)
+      when :abort
+        abort_transaction(name)
+      when :commit
+        commit_transaction(name)
+      when :name
+        transaction_name
+      when nil
+        transaction_open?(name)
+      end
+    end
+
+    def __abort_transaction(name = nil) #:nodoc:
+      @__transaction_checkpoint__ = __rewind_this_transaction
+
+      if name.nil?
+        s = ""
+      else
+        s = "(#{name.inspect})"
+      end
+
+      Transaction::Simple.debug_io << "#{'<' * @__transaction_level__} Abort Transaction#{s}\n" unless Transaction::Simple.debug_io.nil?
+      @__transaction_level__ -= 1
+      @__transaction_names__.pop
+      if @__transaction_level__ < 1
+        @__transaction_level__ = 0
+        @__transaction_names__ = []
+      end
+    end
+
+    TRANSACTION_CHECKPOINT  = "@__transaction_checkpoint__" #:nodoc:
+    SKIP_TRANSACTION_VARS   = [TRANSACTION_CHECKPOINT, "@__transaction_level__"] #:nodoc:
+
+    def __rewind_this_transaction #:nodoc:
+      r = Marshal.restore(@__transaction_checkpoint__)
+
+      begin
+        self.replace(r) if respond_to?(:replace)
+      rescue
+        nil
+      end
+
+      r.instance_variables.each do |i|
+        next if SKIP_TRANSACTION_VARS.include?(i)
+        if respond_to?(:instance_variable_get)
+          instance_variable_set(i, r.instance_variable_get(i))
+        else
+          instance_eval(%q|#{i} = r.instance_eval("#{i}")|)
+        end
+      end
+
+      if respond_to?(:instance_variable_get)
+        return r.instance_variable_get(TRANSACTION_CHECKPOINT)
+      else
+        return r.instance_eval(TRANSACTION_CHECKPOINT)
+      end
+    end
+
+    def __commit_transaction #:nodoc:
+      if respond_to?(:instance_variable_get)
+        @__transaction_checkpoint__ = Marshal.restore(@__transaction_checkpoint__).instance_variable_get(TRANSACTION_CHECKPOINT)
+      else
+        @__transaction_checkpoint__ = Marshal.restore(@__transaction_checkpoint__).instance_eval(TRANSACTION_CHECKPOINT)
+      end
+
+      @__transaction_level__ -= 1
+      @__transaction_names__.pop
+      if @__transaction_level__ < 1
+        @__transaction_level__ = 0
+        @__transaction_names__ = []
+      end
+    end
+
+    private :__abort_transaction, :__rewind_this_transaction, :__commit_transaction
+
+      # = Transaction::Simple::ThreadSafe
+      # Thread-safe simple object transaction support for Ruby.
+      # Transaction::Simple::ThreadSafe is used in the same way as
+      # Transaction::Simple. Transaction::Simple::ThreadSafe uses a Mutex
+      # object to ensure atomicity at the cost of performance in threaded
+      # applications.
+      #
+      # Transaction::Simple::ThreadSafe will not wait to obtain a lock; if the
+      # lock cannot be obtained immediately, a
+      # Transaction::TransactionThreadError will be raised.
+      #
+      # Thanks to Mauricio Fernández for help with getting this part working.
+    module ThreadSafe
+      VERSION = '1.1.1.0';
+
+      include Transaction::Simple
+
+      SKIP_TRANSACTION_VARS = Transaction::Simple::SKIP_TRANSACTION_VARS.dup #:nodoc:
+      SKIP_TRANSACTION_VARS << "@__transaction_mutex__"
+
+      Transaction::Simple.instance_methods(false) do |meth|
+        next if meth == "transaction"
+        arg = "(name = nil)" unless meth == "transaction_name"
+        module_eval <<-EOS
+          def #{meth}#{arg}
+            if (@__transaction_mutex__ ||= Mutex.new).try_lock
+              result = super
+              @__transaction_mutex__.unlock
+              return result
+            else
+              raise TransactionThreadError, "Transaction Error: Cannot obtain lock for ##{meth}"
+            end
+          ensure
+            @__transaction_mutex__.unlock
+          end
+        EOS
+      end
+    end
+  end
+end
+
+if $0 == __FILE__
+  require 'test/unit'
+
+  class Test__Transaction_Simple < Test::Unit::TestCase #:nodoc:
+    VALUE = "Now is the time for all good men to come to the aid of their country."
+
+    def setup
+      @value = VALUE.dup
+      @value.extend(Transaction::Simple)
+    end
+
+    def test_extended
+      assert_respond_to(@value, :start_transaction)
+    end
+
+    def test_started
+      assert_equal(false, @value.transaction_open?)
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+    end
+
+    def test_rewind
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.rewind_transaction }
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_not_equal(VALUE, @value)
+      assert_nothing_raised { @value.rewind_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_equal(VALUE, @value)
+    end
+
+    def test_abort
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.abort_transaction }
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_not_equal(VALUE, @value)
+      assert_nothing_raised { @value.abort_transaction }
+      assert_equal(false, @value.transaction_open?)
+      assert_equal(VALUE, @value)
+    end
+
+    def test_commit
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.commit_transaction }
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_not_equal(VALUE, @value)
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.commit_transaction }
+      assert_equal(false, @value.transaction_open?)
+      assert_not_equal(VALUE, @value)
+    end
+
+    def test_multilevel
+      assert_equal(false, @value.transaction_open?)
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_equal(VALUE.gsub(/men/, 'women'), @value)
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.start_transaction }
+      assert_nothing_raised { @value.gsub!(/country/, 'nation-state') }
+      assert_nothing_raised { @value.commit_transaction }
+      assert_equal(VALUE.gsub(/men/, 'women').gsub(/country/, 'nation-state'), @value)
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.abort_transaction }
+      assert_equal(VALUE, @value)
+    end
+
+    def test_multilevel_named
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.transaction_name }
+      assert_nothing_raised { @value.start_transaction(:first) } # 1
+      assert_raises(Transaction::TransactionError) { @value.start_transaction(:first) }
+      assert_equal(true, @value.transaction_open?)
+      assert_equal(true, @value.transaction_open?(:first))
+      assert_equal(:first, @value.transaction_name)
+      assert_nothing_raised { @value.start_transaction } # 2
+      assert_not_equal(:first, @value.transaction_name)
+      assert_equal(nil, @value.transaction_name)
+      assert_raises(Transaction::TransactionError) { @value.abort_transaction(:second) }
+      assert_nothing_raised { @value.abort_transaction(:first) }
+      assert_equal(false, @value.transaction_open?)
+      assert_nothing_raised do
+        @value.start_transaction(:first)
+        @value.gsub!(/men/, 'women')
+        @value.start_transaction(:second)
+        @value.gsub!(/women/, 'people')
+        @value.start_transaction
+        @value.gsub!(/people/, 'sentients')
+      end
+      assert_nothing_raised { @value.abort_transaction(:second) }
+      assert_equal(true, @value.transaction_open?(:first))
+      assert_equal(VALUE.gsub(/men/, 'women'), @value)
+      assert_nothing_raised do
+        @value.start_transaction(:second)
+        @value.gsub!(/women/, 'people')
+        @value.start_transaction
+        @value.gsub!(/people/, 'sentients')
+      end
+      assert_raises(Transaction::TransactionError) { @value.rewind_transaction(:foo) }
+      assert_nothing_raised { @value.rewind_transaction(:second) }
+      assert_equal(VALUE.gsub(/men/, 'women'), @value)
+      assert_nothing_raised do
+        @value.gsub!(/women/, 'people')
+        @value.start_transaction
+        @value.gsub!(/people/, 'sentients')
+      end
+      assert_raises(Transaction::TransactionError) { @value.commit_transaction(:foo) }
+      assert_nothing_raised { @value.commit_transaction(:first) }
+      assert_equal(VALUE.gsub(/men/, 'sentients'), @value)
+      assert_equal(false, @value.transaction_open?)
+    end
+
+    def test_array
+      assert_nothing_raised do
+        @orig = ["first", "second", "third"]
+        @value = ["first", "second", "third"]
+        @value.extend(Transaction::Simple)
+      end
+      assert_equal(@orig, @value)
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value[1].gsub!(/second/, "fourth") }
+      assert_not_equal(@orig, @value)
+      assert_nothing_raised { @value.abort_transaction }
+      assert_equal(@orig, @value)
+    end
+  end
+
+  class Test__Transaction_Simple_ThreadSafe < Test::Unit::TestCase #:nodoc:
+    VALUE = "Now is the time for all good men to come to the aid of their country."
+
+    def setup
+      @value = VALUE.dup
+      @value.extend(Transaction::Simple::ThreadSafe)
+    end
+
+    def test_extended
+      assert_respond_to(@value, :start_transaction)
+    end
+
+    def test_started
+      assert_equal(false, @value.transaction_open?)
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+    end
+
+    def test_rewind
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.rewind_transaction }
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_not_equal(VALUE, @value)
+      assert_nothing_raised { @value.rewind_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_equal(VALUE, @value)
+    end
+
+    def test_abort
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.abort_transaction }
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_not_equal(VALUE, @value)
+      assert_nothing_raised { @value.abort_transaction }
+      assert_equal(false, @value.transaction_open?)
+      assert_equal(VALUE, @value)
+    end
+
+    def test_commit
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.commit_transaction }
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_not_equal(VALUE, @value)
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.commit_transaction }
+      assert_equal(false, @value.transaction_open?)
+      assert_not_equal(VALUE, @value)
+    end
+
+    def test_multilevel
+      assert_equal(false, @value.transaction_open?)
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.gsub!(/men/, 'women') }
+      assert_equal(VALUE.gsub(/men/, 'women'), @value)
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.start_transaction }
+      assert_nothing_raised { @value.gsub!(/country/, 'nation-state') }
+      assert_nothing_raised { @value.commit_transaction }
+      assert_equal(VALUE.gsub(/men/, 'women').gsub(/country/, 'nation-state'), @value)
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value.abort_transaction }
+      assert_equal(VALUE, @value)
+    end
+
+    def test_multilevel_named
+      assert_equal(false, @value.transaction_open?)
+      assert_raises(Transaction::TransactionError) { @value.transaction_name }
+      assert_nothing_raised { @value.start_transaction(:first) } # 1
+      assert_raises(Transaction::TransactionError) { @value.start_transaction(:first) }
+      assert_equal(true, @value.transaction_open?)
+      assert_equal(true, @value.transaction_open?(:first))
+      assert_equal(:first, @value.transaction_name)
+      assert_nothing_raised { @value.start_transaction } # 2
+      assert_not_equal(:first, @value.transaction_name)
+      assert_equal(nil, @value.transaction_name)
+      assert_raises(Transaction::TransactionError) { @value.abort_transaction(:second) }
+      assert_nothing_raised { @value.abort_transaction(:first) }
+      assert_equal(false, @value.transaction_open?)
+      assert_nothing_raised do
+        @value.start_transaction(:first)
+        @value.gsub!(/men/, 'women')
+        @value.start_transaction(:second)
+        @value.gsub!(/women/, 'people')
+        @value.start_transaction
+        @value.gsub!(/people/, 'sentients')
+      end
+      assert_nothing_raised { @value.abort_transaction(:second) }
+      assert_equal(true, @value.transaction_open?(:first))
+      assert_equal(VALUE.gsub(/men/, 'women'), @value)
+      assert_nothing_raised do
+        @value.start_transaction(:second)
+        @value.gsub!(/women/, 'people')
+        @value.start_transaction
+        @value.gsub!(/people/, 'sentients')
+      end
+      assert_raises(Transaction::TransactionError) { @value.rewind_transaction(:foo) }
+      assert_nothing_raised { @value.rewind_transaction(:second) }
+      assert_equal(VALUE.gsub(/men/, 'women'), @value)
+      assert_nothing_raised do
+        @value.gsub!(/women/, 'people')
+        @value.start_transaction
+        @value.gsub!(/people/, 'sentients')
+      end
+      assert_raises(Transaction::TransactionError) { @value.commit_transaction(:foo) }
+      assert_nothing_raised { @value.commit_transaction(:first) }
+      assert_equal(VALUE.gsub(/men/, 'sentients'), @value)
+      assert_equal(false, @value.transaction_open?)
+    end
+
+    def test_array
+      assert_nothing_raised do
+        @orig = ["first", "second", "third"]
+        @value = ["first", "second", "third"]
+        @value.extend(Transaction::Simple::ThreadSafe)
+      end
+      assert_equal(@orig, @value)
+      assert_nothing_raised { @value.start_transaction }
+      assert_equal(true, @value.transaction_open?)
+      assert_nothing_raised { @value[1].gsub!(/second/, "fourth") }
+      assert_not_equal(@orig, @value)
+      assert_nothing_raised { @value.abort_transaction }
+      assert_equal(@orig, @value)
+    end
+  end
+end