test/ruby/test_undef.rb


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# frozen_string_literal: false
require 'test/unit'

class TestUndef < Test::Unit::TestCase
  class Undef0
    def foo
      "foo"
    end
    undef foo
  end

  class Undef1
    def bar
      "bar"
    end
  end

  class Undef2 < Undef1
    undef bar
  end

  def test_undef
    x = Undef0.new
    assert_raise(NoMethodError) { x.foo }
    y = Undef1.new
    assert_equal "bar", y.bar
    z = Undef2.new
    assert_raise(NoMethodError) { z.bar }
  end

  def test_special_const_undef
    assert_raise(TypeError) do
      1.instance_eval do
        undef to_s
      end
    end
  end

  def test_singleton_undef
    klass = Class.new do
      def foo
        :ok
      end
    end

    klass.new.foo

    klass.new.instance_eval do
      undef foo
    end

    klass.new.foo
  end
end