truncate table rather than delete_all in specs

This shaves a few seconds off each selenium spec in my local env

Change-Id: I73af04e18a75c5964474bf396ea7bafc8527d384
Reviewed-on: https://gerrit.instructure.com/4083
Tested-by: Hudson <hudson@instructure.com>
Tested-by: Selenium <selenium@instructure.com>
Reviewed-by: JT Olds <jt@instructure.com>

spec/selenium/common.rb

@@ -225,11 +225,11 @@ shared_examples_for "all selenium tests" do
   end
 
   self.use_transactional_fixtures = false
-  
+
   append_after(:each) do
-    ALL_MODELS.each &:delete_all
+    ALL_MODELS.each { |m| truncate_table(m) }
   end
-  
+
   append_before(:all) do
     @selenium_driver = setup_selenium
   end

spec/spec_helper.rb

@@ -30,10 +30,6 @@ ALL_MODELS = Dir.glob(File.expand_path(File.dirname(__FILE__) + '/../app/models'
   eval(model) rescue nil
 }.find_all{|x| x.respond_to? :delete_all and x.count >= 0 rescue false}
 
-# wipe out the test db, in case some non-transactional tests crapped out before
-# cleaning up after themselves
-ALL_MODELS.each &:delete_all
-
 # rspec aliases :describe to :context in a way that it's pretty much defined
 # globally on every object. :context is already heavily used in our application,
 # so we remove rspec's definition.
@@ -41,6 +37,19 @@ module Spec::DSL::Main
   remove_method :context
 end
 
+def truncate_table(model)
+  case model.connection.adapter_name
+  when "SQLite"
+    model.delete_all
+  else
+    model.connection.execute("TRUNCATE TABLE #{model.connection.quote_table_name(model.table_name)}")
+  end
+end
+
+# wipe out the test db, in case some non-transactional tests crapped out before
+# cleaning up after themselves
+ALL_MODELS.each { |m| truncate_table(m) }
+
 Spec::Runner.configure do |config|
   # If you're not using ActiveRecord you should remove these
   # lines, delete config/database.yml and disable :active_record