allow setting of orm and skip autodetect

lib/database_cleaner/configuration.rb

@@ -26,6 +26,10 @@ module DatabaseCleaner
        end
     end
 
+    def orm=(orm_string)
+      @orm = orm_string
+    end
+
     def start
       strategy.start
     end
@@ -50,6 +54,7 @@ module DatabaseCleaner
 
 
     def orm
+      @orm ||=begin
                  if defined? ::ActiveRecord
                   'active_record'
                 elsif defined? ::DataMapper
@@ -58,6 +63,7 @@ module DatabaseCleaner
                   raise NoORMDetected, "No known ORM was detected!  Is ActiveRecord or DataMapper loaded?"
                 end
               end
+    end
 
 
     def orm_module

spec/database_cleaner/configuration_spec.rb

@@ -7,6 +7,7 @@ describe DatabaseCleaner do
     DatabaseCleaner::ActiveRecord::Transaction.stub!(:new).and_return(@strategy = mock('strategy'))
     Object.const_set('ActiveRecord', "just mocking out the constant here...") unless defined?(::ActiveRecord)
     DatabaseCleaner.strategy = nil
+    DatabaseCleaner.orm = nil
   end
 
   describe ".strategy=" do
@@ -16,6 +17,7 @@ describe DatabaseCleaner do
 
       Object.send(:remove_const, 'ActiveRecord')
       Object.const_set('DataMapper', "just mocking out the constant here...")
+      DatabaseCleaner.orm = nil
 
       DatabaseCleaner::DataMapper::Transaction.should_receive(:new).with(no_args)
       DatabaseCleaner.strategy = :transaction
@@ -28,6 +30,13 @@ describe DatabaseCleaner do
       running { DatabaseCleaner.strategy = :transaction }.should raise_error(DatabaseCleaner::NoORMDetected)
     end
 
+    it "should use the strategy version of the ORM specified with #orm=" do
+      DatabaseCleaner.orm = 'data_mapper'
+      DatabaseCleaner::DataMapper::Transaction.should_receive(:new)
+
+      DatabaseCleaner.strategy = :transaction
+    end
+
     it "should raise an error when the specified strategy is not found" do
       running { DatabaseCleaner.strategy = :foo }.should raise_error(DatabaseCleaner::UnknownStrategySpecified)
     end