Finished porting over MySQL import functionality.

* removed assertions on #num_inserts, that is db-specific and is handled in details by abstract_adapter_test.

test/support/mysql/assertions.rb

@@ -0,0 +1,55 @@
+class ActiveSupport::TestCase
+  module MySQLAssertions
+    def self.extended(klass)
+      klass.instance_eval do
+        assertion(:should_not_update_created_at_on_timestamp_columns) do
+          Delorean.time_travel_to("5 minutes from now") do
+            perform_import
+            assert_equal @topic.created_at.to_i, updated_topic.created_at.to_i
+            assert_equal @topic.created_on.to_i, updated_topic.created_on.to_i
+          end
+        end
+
+        assertion(:should_update_updated_at_on_timestamp_columns) do
+          time = Chronic.parse("5 minutes from now")
+          Delorean.time_travel_to(time) do
+            perform_import
+            assert_equal time.to_i, updated_topic.updated_at.to_i
+            assert_equal time.to_i, updated_topic.updated_on.to_i
+          end
+        end
+
+        assertion(:should_not_update_timestamps) do
+          Delorean.time_travel_to("5 minutes from now") do
+            perform_import :timestamps => false
+            assert_equal @topic.created_at.to_i, updated_topic.created_at.to_i
+            assert_equal @topic.created_on.to_i, updated_topic.created_on.to_i
+            assert_equal @topic.updated_at.to_i, updated_topic.updated_at.to_i
+            assert_equal @topic.updated_on.to_i, updated_topic.updated_on.to_i
+          end
+        end
+
+        assertion(:should_not_update_fields_not_mentioned) do
+          assert_equal "John Doe", updated_topic.author_name
+        end
+
+        assertion(:should_update_fields_mentioned) do
+          perform_import
+          assert_equal "Book - 2nd Edition", updated_topic.title
+          assert_equal "johndoe@example.com", updated_topic.author_email_address
+        end
+
+        assertion(:should_update_fields_mentioned_with_hash_mappings) do
+          perform_import
+          assert_equal "johndoe@example.com", updated_topic.title
+          assert_equal "Book - 2nd Edition", updated_topic.author_email_address
+        end
+
+        assertion(:should_update_foreign_keys) do
+          perform_import
+          assert_equal 57, updated_topic.parent_id
+        end
+      end
+    end
+  end
+end