Extracted TruncationBase into own file and only require it for the

strategies that need it.

lib/database_cleaner/active_record/truncation.rb

@@ -1,3 +1,4 @@
+require "database_cleaner/truncation_base"
 
 module ActiveRecord
   module ConnectionAdapters

lib/database_cleaner/configuration.rb

@@ -92,8 +92,6 @@ module DatabaseCleaner
   end
 
 
-  # common base class for truncation strategies
-
   class TruncationBase
 
     def initialize(options = {})

lib/database_cleaner/data_mapper/truncation.rb

@@ -1,3 +1,5 @@
+require "database_cleaner/truncation_base"
+
 module DataMapper
   module Adapters
 

lib/database_cleaner/truncation_base.rb

@@ -0,0 +1,40 @@
+class TruncationBase
+
+  def initialize(options = {})
+    if !options.empty? && !(options.keys - [:only, :except]).empty?
+      raise ArgumentError, "The only valid options are :only and :except. You specified #{options.keys.join(',')}."
+    end
+    if options.has_key?(:only) && options.has_key?(:except)
+      raise ArgumentError, "You may only specify either :only or :either.  Doing both doesn't really make sense does it?"
+    end
+
+    @only = options[:only]
+    @tables_to_exclude = (options[:except] || [])
+    if migration_storage = migration_storage_name
+      @tables_to_exclude << migration_storage
+    end
+  end
+
+  def start
+    # no-op
+  end
+
+  def clean
+    raise NotImplementedError
+  end
+
+
+  private
+
+  def tables_to_truncate
+    raise NotImplementedError
+  end
+
+  # overwrite in subclasses
+  # default implementation given because migration storage need not be present
+  def migration_storage_name
+    nil
+  end
+
+end
+