1 files changed, 11 insertions, 0 deletions
diff --git a/activerecord/test/models/lesson.rb b/activerecord/test/models/lesson.rb
new file mode 100644
index 0000000000..4c88153068
--- /dev/null
+++ b/activerecord/test/models/lesson.rb
@@ -0,0 +1,11 @@
+class LessonError < Exception
+end
+
+class Lesson < ActiveRecord::Base
+  has_and_belongs_to_many :students
+  before_destroy :ensure_no_students
+
+  def ensure_no_students
+    raise LessonError unless students.empty?
+  end
+end