```ruby
module Petitest
  class TestGroup
    include ::Petitest::Assertions

    TEST_METHOD_NAME_PREFIX = "test_"

    class << self
      # @return [Array<Class>]
      def descendants
        @@descendants ||= []
      end

      # @note Override
      def inherited(sub_class)
        super
        descendants << sub_class
      end

      # @note Override
      def method_added(method_name)
        super
        if method_name.to_s.start_with?(TEST_METHOD_NAME_PREFIX)
          caller_location = caller_locations(1, 1)[0]
          test_methods << ::Petitest::TestMethod.new(
            line_number: caller_location.lineno,
            method_name: method_name.to_s,
            path: ::File.expand_path(caller_location.absolute_path || caller_location.path)
          )
        end
      end

      # @return [Array<Petitest::TestMethod>]
      def test_methods
        @test_methods ||= []
      end
    end
  end
end
```

Use public_instance_methods instead of method_added
user
```ruby
module Petitest
  class TestGroup
    include ::Petitest::Assertions

    TEST_METHOD_NAME_PREFIX = "test_"

    class << self
      # @return [Array<Class>]
      def descendants
        @@descendants ||= []
      end

      # @note Override
      def inherited(sub_class)
        super
        descendants << sub_class
      end

      # @return [Array<Petitest::TestMethod>]
      def test_methods
        public_instance_methods.map(&:to_s).select do |method_name|
          method_name.start_with?(TEST_METHOD_NAME_PREFIX)
        end.map do |method_name|
          unbound_method = public_instance_method(method_name)
          ::Petitest::TestMethod.new(
            line_number: unbound_method.source_location[1],
            method_name: method_name.to_s,
            path: unbound_method.source_location[0],
          )
        end
      end
    end
  end
end
```
assistant