testing a non-invertible migration case

activerecord/test/cases/invertable_migration_test.rb

@@ -2,16 +2,28 @@ require "cases/helper"
 
 module ActiveRecord
   class InvertableMigrationTest < ActiveRecord::TestCase
-    class InvertableMigration < ActiveRecord::Migration
+    class SilentMigration < ActiveRecord::Migration
+      def write(text = '')
+        # sssshhhhh!!
+      end
+    end
+
+    class InvertableMigration < SilentMigration
       def change
         create_table("horses") do |t|
           t.column :content, :text
           t.column :remind_at, :datetime
         end
       end
+    end
 
-      def write(text = '')
-        # sssshhhhh!!
+    class NonInvertableMigration < SilentMigration
+      def change
+        create_table("horses") do |t|
+          t.column :content, :text
+          t.column :remind_at, :datetime
+        end
+        remove_column "horses", :content
       end
     end
 
@@ -21,6 +33,14 @@ module ActiveRecord
       end
     end
 
+    def test_no_reverse
+      migration = NonInvertableMigration.new
+      migration.migrate(:up)
+      assert_raises(IrreversibleMigration) do
+        migration.migrate(:down)
+      end
+    end
+
     def test_up
       migration = InvertableMigration.new
       migration.migrate(:up)