fix typo and add a test

Author: ko1

lib/debug/session.rb

@@ -1665,7 +1665,7 @@ def method_added tp
         case mid
         when :method_added, :singleton_method_added
           Session.create_method_added_tracker(tp.self, mid)
-          Session.create_method_added_tracker unless resolved
+          Session.activate_method_added_trackers unless resolved
         end
       end
     end

test/console/break_test.rb

@@ -527,6 +527,32 @@ def test_break_with_class_method_stops_at_correct_place
     end
   end
 
+  class MethodAddedTest < ConsoleTestCase
+    def program_method_added
+      <<~RUBY
+         1| class C
+         2|   def self.method_added mid
+         3|     debugger
+         4|   end
+         5|   def foo
+         6|   end
+         5| end
+         6| C.new.foo
+      RUBY
+    end
+
+    def test_break_after_user_defined_method_added
+      debug_code program_method_added do
+        type 'b C#foo'
+        type 'c'
+        assert_line_num 3
+        type 'c'
+        assert_line_num 5
+        type 'c'
+      end
+    end
+  end
+
   #
   # Tests adding breakpoints to lines
   #