ruby--ruby/test/ruby/test_exception.rb

# frozen_string_literal: false
require 'test/unit'
require 'tempfile'

class TestException < Test::Unit::TestCase
  def test_exception_rescued
    begin
      raise "this must be handled"
      assert(false)
    rescue
      assert(true)
    end
  end

  def test_exception_retry
    bad = true
    begin
      raise "this must be handled no.2"
    rescue
      if bad
        bad = false
        retry
      end
      assert(!bad)
    end
    assert(true)
  end

  def test_exception_in_rescue
    string = "this must be handled no.3"
    assert_raise_with_message(RuntimeError, string) do
      begin
        raise "exception in rescue clause"
      rescue
        raise string
      end
      assert(false)
    end
  end

  def test_exception_in_ensure
    string = "exception in ensure clause"
    assert_raise_with_message(RuntimeError, string) do
      begin
        raise "this must be handled no.4"
      ensure
        assert_instance_of(RuntimeError, $!)
        assert_equal("this must be handled no.4", $!.message)
        raise "exception in ensure clause"
      end
      assert(false)
    end
  end

  def test_exception_ensure
    bad = true
    begin
      begin
        raise "this must be handled no.5"
      ensure
        bad = false
      end
    rescue
    end
    assert(!bad)
  end

  def test_exception_ensure_2   # just duplication?
    bad = true
    begin
      begin
        raise "this must be handled no.6"
      ensure
        bad = false
      end
    rescue
    end
    assert(!bad)
  end

  def test_errinfo_in_debug
    bug9568 = EnvUtil.labeled_class("[ruby-core:61091] [Bug #9568]", RuntimeError) do
      def to_s
        require '\0'
      rescue LoadError
        self.class.to_s
      end
    end

    err = EnvUtil.verbose_warning do
      assert_raise(bug9568) do
        $DEBUG, debug = true, $DEBUG
        begin
          raise bug9568
        ensure
          $DEBUG = debug
        end
      end
    end
    assert_include(err, bug9568.to_s)
  end

  def test_errinfo_encoding_in_debug
    exc = Module.new {break class_eval("class C\u{30a8 30e9 30fc} < RuntimeError; self; end".encode(Encoding::EUC_JP))}
    exc.inspect

    err = EnvUtil.verbose_warning do
      assert_raise(exc) do
        $DEBUG, debug = true, $DEBUG
        begin
          raise exc
        ensure
          $DEBUG = debug
        end
      end
    end
    assert_include(err, exc.to_s)
  end

  def test_break_ensure
    bad = true
    while true
      begin
        break
      ensure
        bad = false
      end
    end
    assert(!bad)
  end

  def test_catch_no_throw
    assert_equal(:foo, catch {:foo})
  end

  def test_catch_throw
    result = catch(:foo) {
      loop do
        loop do
          throw :foo, true
          break
        end
        assert(false, "should not reach here")
      end
      false
    }
    assert(result)
  end

  def test_catch_throw_noarg
    assert_nothing_raised(UncaughtThrowError) {
      result = catch {|obj|
        throw obj, :ok
        assert(false, "should not reach here")
      }
      assert_equal(:ok, result)
    }
  end

  def test_uncaught_throw
    tag = nil
    e = assert_raise_with_message(UncaughtThrowError, /uncaught throw/) {
      catch("foo") {|obj|
        tag = obj.dup
        throw tag, :ok
        assert(false, "should not reach here")
      }
      assert(false, "should not reach here")
    }
    assert_not_nil(tag)
    assert_same(tag, e.tag)
    assert_equal(:ok, e.value)
  end

  def test_catch_throw_in_require
    bug7185 = '[ruby-dev:46234]'
    Tempfile.create(["dep", ".rb"]) {|t|
      t.puts("throw :extdep, 42")
      t.close
      assert_equal(42, assert_throw(:extdep, bug7185) {require t.path}, bug7185)
    }
  end

  def test_throw_false
    bug12743 = '[ruby-core:77229] [Bug #12743]'
    e = assert_raise_with_message(UncaughtThrowError, /false/, bug12743) {
      Thread.start {
        throw false
      }.join
    }
    assert_same(false, e.tag, bug12743)
  end

  def test_else_no_exception
    begin
      assert(true)
    rescue
      assert(false)
    else
      assert(true)
    end
  end

  def test_else_raised
    begin
      assert(true)
      raise
      assert(false)
    rescue
      assert(true)
    else
      assert(false)
    end
  end

  def test_else_nested_no_exception
    begin
      assert(true)
      begin
	assert(true)
      rescue
	assert(false)
      else
	assert(true)
      end
      assert(true)
    rescue
      assert(false)
    else
      assert(true)
    end
  end

  def test_else_nested_rescued
    begin
      assert(true)
      begin
	assert(true)
	raise
	assert(false)
      rescue
	assert(true)
      else
	assert(false)
      end
      assert(true)
    rescue
      assert(false)
    else
      assert(true)
    end
  end

  def test_else_nested_unrescued
    begin
      assert(true)
      begin
	assert(true)
      rescue
	assert(false)
      else
	assert(true)
      end
      assert(true)
      raise
      assert(false)
    rescue
      assert(true)
    else
      assert(false)
    end
  end

  def test_else_nested_rescued_reraise
    begin
      assert(true)
      begin
	assert(true)
	raise
	assert(false)
      rescue
	assert(true)
      else
	assert(false)
      end
      assert(true)
      raise
      assert(false)
    rescue
      assert(true)
    else
      assert(false)
    end
  end

  def test_raise_with_wrong_number_of_arguments
    assert_raise(TypeError) { raise nil }
    assert_raise(TypeError) { raise 1, 1 }
    assert_raise(ArgumentError) { raise 1, 1, 1, 1 }
  end

  def test_type_error_message_encoding
    c = eval("Module.new do break class C\u{4032}; self; end; end")
    o = c.new
    assert_raise_with_message(TypeError, /C\u{4032}/) do
      ""[o]
    end
    c.class_eval {def to_int; self; end}
    assert_raise_with_message(TypeError, /C\u{4032}/) do
      ""[o]
    end
    c.class_eval {def to_a; self; end}
    assert_raise_with_message(TypeError, /C\u{4032}/) do
      [*o]
    end
    obj = eval("class C\u{1f5ff}; self; end").new
    assert_raise_with_message(TypeError, /C\u{1f5ff}/) do
      Class.new {include obj}
    end
  end

  def test_errat
    assert_in_out_err([], "p $@", %w(nil), [])

    assert_in_out_err([], "$@ = 1", [], /\$! not set \(ArgumentError\)$/)

    assert_in_out_err([], <<-INPUT, [], /backtrace must be Array of String \(TypeError\)$/)
      begin
        raise
      rescue
        $@ = 1
      end
    INPUT

    assert_in_out_err([], <<-INPUT, [], /^foo: unhandled exception$/)
      begin
        raise
      rescue
        $@ = 'foo'
        raise
      end
    INPUT

    assert_in_out_err([], <<-INPUT, [], /^foo: unhandled exception\s+from bar\s+from baz$/)
      begin
        raise
      rescue
        $@ = %w(foo bar baz)
        raise
      end
    INPUT
  end

  def test_thread_signal_location
    _, stderr, _ = EnvUtil.invoke_ruby(%w"--disable-gems -d", <<-RUBY, false, true)
Thread.start do
  begin
    Process.kill(:INT, $$)
  ensure
    raise "in ensure"
  end
end.join
    RUBY
    assert_not_match(/:0/, stderr, "[ruby-dev:39116]")
  end

  def test_errinfo
    begin
      raise "foo"
      assert(false)
    rescue => e
      assert_equal(e, $!)
      1.times { assert_equal(e, $!) }
    end

    assert_equal(nil, $!)
  end

  def test_inspect
    assert_equal("#<Exception: Exception>", Exception.new.inspect)

    e = Class.new(Exception)
    e.class_eval do
      def to_s; ""; end
    end
    assert_equal(e.inspect, e.new.inspect)
  end

  def test_to_s
    e = StandardError.new("foo")
    assert_equal("foo", e.to_s)

    def (s = Object.new).to_s
      "bar"
    end
    e = StandardError.new(s)
    assert_equal("bar", e.to_s)
  end

  def test_set_backtrace
    e = Exception.new

    e.set_backtrace("foo")
    assert_equal(["foo"], e.backtrace)

    e.set_backtrace(%w(foo bar baz))
    assert_equal(%w(foo bar baz), e.backtrace)

    assert_raise(TypeError) { e.set_backtrace(1) }
    assert_raise(TypeError) { e.set_backtrace([1]) }
  end

  def test_exit_success_p
    begin
      exit
    rescue SystemExit => e
    end
    assert_send([e, :success?], "success by default")

    begin
      exit(true)
    rescue SystemExit => e
    end
    assert_send([e, :success?], "true means success")

    begin
      exit(false)
    rescue SystemExit => e
    end
    assert_not_send([e, :success?], "false means failure")

    begin
      abort
    rescue SystemExit => e
    end
    assert_not_send([e, :success?], "abort means failure")
  end

  def test_nomethoderror
    bug3237 = '[ruby-core:29948]'
    str = "\u2600"
    id = :"\u2604"
    msg = "undefined method `#{id}' for \"#{str}\":String"
    assert_raise_with_message(NoMethodError, msg, bug3237) do
      str.__send__(id)
    end
  end

  def test_errno
    assert_equal(Encoding.find("locale"), Errno::EINVAL.new.message.encoding)
  end

  def test_too_many_args_in_eval
    bug5720 = '[ruby-core:41520]'
    arg_string = (0...140000).to_a.join(", ")
    assert_raise(SystemStackError, bug5720) {eval "raise(#{arg_string})"}
  end

  def test_systemexit_new
    e0 = SystemExit.new
    assert_equal(0, e0.status)
    assert_equal("SystemExit", e0.message)
    ei = SystemExit.new(3)
    assert_equal(3, ei.status)
    assert_equal("SystemExit", ei.message)
    es = SystemExit.new("msg")
    assert_equal(0, es.status)
    assert_equal("msg", es.message)
    eis = SystemExit.new(7, "msg")
    assert_equal(7, eis.status)
    assert_equal("msg", eis.message)

    bug5728 = '[ruby-dev:44951]'
    et = SystemExit.new(true)
    assert_equal(true, et.success?, bug5728)
    assert_equal("SystemExit", et.message, bug5728)
    ef = SystemExit.new(false)
    assert_equal(false, ef.success?, bug5728)
    assert_equal("SystemExit", ef.message, bug5728)
    ets = SystemExit.new(true, "msg")
    assert_equal(true, ets.success?, bug5728)
    assert_equal("msg", ets.message, bug5728)
    efs = SystemExit.new(false, "msg")
    assert_equal(false, efs.success?, bug5728)
    assert_equal("msg", efs.message, bug5728)
  end

  def test_exception_in_name_error_to_str
    bug5575 = '[ruby-core:41612]'
    Tempfile.create(["test_exception_in_name_error_to_str", ".rb"]) do |t|
      t.puts <<-EOC
      begin
        BasicObject.new.inspect
      rescue
        $!.inspect
      end
    EOC
      t.close
      assert_nothing_raised(NameError, bug5575) do
        load(t.path)
      end
    end
  end

  def test_equal
    bug5865 = '[ruby-core:41979]'
    assert_equal(RuntimeError.new("a"), RuntimeError.new("a"), bug5865)
    assert_not_equal(RuntimeError.new("a"), StandardError.new("a"), bug5865)
  end

  def test_exception_in_exception_equal
    bug5865 = '[ruby-core:41979]'
    Tempfile.create(["test_exception_in_exception_equal", ".rb"]) do |t|
      t.puts <<-EOC
      o = Object.new
      def o.exception(arg)
      end
      _ = RuntimeError.new("a") == o
      EOC
      t.close
      assert_nothing_raised(ArgumentError, bug5865) do
        load(t.path)
      end
    end
  end

  Bug4438 = '[ruby-core:35364]'

  def test_rescue_single_argument
    assert_raise(TypeError, Bug4438) do
      begin
        raise
      rescue 1
      end
    end
  end

  def test_rescue_splat_argument
    assert_raise(TypeError, Bug4438) do
      begin
        raise
      rescue *Array(1)
      end
    end
  end

  def test_to_s_taintness_propagation
    for exc in [Exception, NameError]
      m = "abcdefg"
      e = exc.new(m)
      e.taint
      s = e.to_s
      assert_equal(false, m.tainted?,
                   "#{exc}#to_s should not propagate taintness")
      assert_equal(false, s.tainted?,
                   "#{exc}#to_s should not propagate taintness")
    end

    o = Object.new
    def o.to_str
      "foo"
    end
    o.taint
    e = NameError.new(o)
    s = e.to_s
    assert_equal(false, s.tainted?)
  end

  def m
    m(&->{return 0})
    42
  end

  def test_stackoverflow
    feature6216 = '[ruby-core:43794] [Feature #6216]'
    e = assert_raise(SystemStackError, feature6216) {m}
    level = e.backtrace.size
    assert_operator(level, :>, 10, feature6216)

    feature6216 = '[ruby-core:63377] [Feature #6216]'
    e = assert_raise(SystemStackError, feature6216) {raise e}
    assert_equal(level, e.backtrace.size, feature6216)
  end

  def test_machine_stackoverflow
    bug9109 = '[ruby-dev:47804] [Bug #9109]'
    assert_separately(%w[--disable-gem], <<-SRC)
    assert_raise(SystemStackError, #{bug9109.dump}) {
      h = {a: ->{h[:a].call}}
      h[:a].call
    }
    SRC
  rescue SystemStackError
  end

  def test_machine_stackoverflow_by_define_method
    bug9454 = '[ruby-core:60113] [Bug #9454]'
    assert_separately(%w[--disable-gem], <<-SRC)
    assert_raise(SystemStackError, #{bug9454.dump}) {
      define_method(:foo) {self.foo}
      self.foo
    }
    SRC
  rescue SystemStackError
  end

  def test_machine_stackoverflow_by_trace
    assert_normal_exit("#{<<-"begin;"}\n#{<<~"end;"}", timeout: 60)
    begin;
      require 'timeout'
      require 'tracer'
      class HogeError < StandardError
        def to_s
          message.upcase        # disable tailcall optimization
        end
      end
      Tracer.stdout = open(IO::NULL, "w")
      begin
        Timeout.timeout(5) do
          Tracer.on
          HogeError.new.to_s
        end
      rescue Timeout::Error
        # ok. there are no SEGV or critical error
      rescue SystemStackError => e
        # ok.
      end
    end;
  end

  def test_cause
    msg = "[Feature #8257]"
    cause = nil
    e = assert_raise(StandardError) {
      begin
        raise msg
      rescue => e
        cause = e.cause
        raise StandardError
      end
    }
    assert_nil(cause, msg)
    cause = e.cause
    assert_instance_of(RuntimeError, cause, msg)
    assert_equal(msg, cause.message, msg)
  end

  def test_cause_reraised
    msg = "[Feature #8257]"
    e = assert_raise(RuntimeError) {
      begin
        raise msg
      rescue => e
        raise e
      end
    }
    assert_not_same(e, e.cause, "#{msg}: should not be recursive")
  end

  def test_cause_raised_in_rescue
    a = nil
    e = assert_raise_with_message(RuntimeError, 'b') {
      begin
        raise 'a'
      rescue => a
        begin
          raise 'b'
        rescue => b
          assert_same(a, b.cause)
          begin
            raise 'c'
          rescue
            raise b
          end
        end
      end
    }
    assert_same(a, e.cause, 'cause should not be overwritten by reraise')
  end

  def test_cause_at_raised
    a = nil
    e = assert_raise_with_message(RuntimeError, 'b') {
      begin
        raise 'a'
      rescue => a
        b = RuntimeError.new('b')
        assert_nil(b.cause)
        begin
          raise 'c'
        rescue
          raise b
        end
      end
    }
    assert_equal('c', e.cause.message, 'cause should be the exception at raised')
    assert_same(a, e.cause.cause)
  end

  def test_raise_with_cause
    msg = "[Feature #8257]"
    cause = ArgumentError.new("foobar")
    e = assert_raise(RuntimeError) {raise msg, cause: cause}
    assert_same(cause, e.cause)
  end

  def test_cause_with_no_arguments
    cause = ArgumentError.new("foobar")
    assert_raise_with_message(ArgumentError, /with no arguments/) do
      raise cause: cause
    end
  end

  def test_raise_with_cause_in_rescue
    e = assert_raise_with_message(RuntimeError, 'b') {
      begin
        raise 'a'
      rescue => a
        begin
          raise 'b'
        rescue => b
          assert_same(a, b.cause)
          begin
            raise 'c'
          rescue
            raise b, cause: ArgumentError.new('d')
          end
        end
      end
    }
    assert_equal('d', e.cause.message, 'cause option should be honored always')
    assert_nil(e.cause.cause)
  end

  def test_cause_thread_no_cause
    bug12741 = '[ruby-core:77222] [Bug #12741]'

    x = Thread.current
    a = false
    y = Thread.start do
      Thread.pass until a
      x.raise "stop"
    end

    begin
      raise bug12741
    rescue
      e = assert_raise_with_message(RuntimeError, "stop") do
        a = true
        sleep 1
      end
    end
    assert_nil(e.cause)
  ensure
    y.join
  end

  def test_cause_thread_with_cause
    bug12741 = '[ruby-core:77222] [Bug #12741]'

    x = Thread.current
    q = Queue.new
    y = Thread.start do
      q.pop
      begin
        raise "caller's cause"
      rescue
        x.raise "stop"
      end
    end

    begin
      raise bug12741
    rescue
      e = assert_raise_with_message(RuntimeError, "stop") do
        q.push(true)
        sleep 1
      end
    ensure
      y.join
    end
    assert_equal("caller's cause", e.cause.message)
  end

  def test_unknown_option
    bug = '[ruby-core:63203] [Feature #8257] should pass unknown options'

    exc = Class.new(RuntimeError) do
      attr_reader :arg
      def initialize(msg = nil)
        @arg = msg
        super(msg)
      end
    end

    e = assert_raise(exc, bug) {raise exc, "foo" => "bar", foo: "bar"}
    assert_equal({"foo" => "bar", foo: "bar"}, e.arg, bug)

    e = assert_raise(exc, bug) {raise exc, "foo" => "bar", foo: "bar", cause: "zzz"}
    assert_equal({"foo" => "bar", foo: "bar"}, e.arg, bug)

    e = assert_raise(exc, bug) {raise exc, {}}
    assert_equal({}, e.arg, bug)
  end

  def test_circular_cause
    bug13043 = '[ruby-core:78688] [Bug #13043]'
    begin
      begin
        raise "error 1"
      ensure
        orig_error = $!
        begin
          raise "error 2"
        rescue => err
          raise orig_error
        end
      end
    rescue => x
    end
    assert_equal(orig_error, x)
    assert_equal(orig_error, err.cause)
    assert_nil(orig_error.cause, bug13043)
  end

  def test_cause_with_frozen_exception
    exc = ArgumentError.new("foo").freeze
    assert_raise_with_message(ArgumentError, exc.message) {
      raise exc, cause: RuntimeError.new("bar")
    }
  end

  def test_anonymous_message
    assert_in_out_err([], "raise Class.new(RuntimeError), 'foo'", [], /foo\n/)
  end

  PrettyObject =
    Class.new(BasicObject) do
      alias object_id __id__
      def pretty_inspect; "`obj'"; end
      alias inspect pretty_inspect
    end

  def test_name_error_info_const
    obj = PrettyObject.new

    e = assert_raise(NameError) {
      obj.instance_eval("Object")
    }
    assert_equal(:Object, e.name)

    e = assert_raise(NameError) {
      BasicObject::X
    }
    assert_same(BasicObject, e.receiver)
    assert_equal(:X, e.name)
  end

  def test_name_error_info_method
    obj = PrettyObject.new

    e = assert_raise(NameError) {
      obj.instance_eval {foo}
    }
    assert_equal(:foo, e.name)
    assert_same(obj, e.receiver)

    e = assert_raise(NoMethodError) {
      obj.foo(1, 2)
    }
    assert_equal(:foo, e.name)
    assert_equal([1, 2], e.args)
    assert_same(obj, e.receiver)
    assert_not_predicate(e, :private_call?)

    e = assert_raise(NoMethodError) {
      obj.instance_eval {foo(1, 2)}
    }
    assert_equal(:foo, e.name)
    assert_equal([1, 2], e.args)
    assert_same(obj, e.receiver)
    assert_predicate(e, :private_call?)
  end

  def test_name_error_info_local_variables
    obj = PrettyObject.new
    def obj.test(a, b=nil, *c, &d)
      e = a
      1.times {|f| g = foo; g}
      e
    end

    e = assert_raise(NameError) {
      obj.test(3)
    }
    assert_equal(:foo, e.name)
    assert_same(obj, e.receiver)
    assert_equal(%i[a b c d e f g], e.local_variables.sort)
  end

  def test_name_error_info_method_missing
    obj = PrettyObject.new
    def obj.method_missing(*)
      super
    end

    e = assert_raise(NoMethodError) {
      obj.foo(1, 2)
    }
    assert_equal(:foo, e.name)
    assert_equal([1, 2], e.args)
    assert_same(obj, e.receiver)
    assert_not_predicate(e, :private_call?)

    e = assert_raise(NoMethodError) {
      obj.instance_eval {foo(1, 2)}
    }
    assert_equal(:foo, e.name)
    assert_equal([1, 2], e.args)
    assert_same(obj, e.receiver)
    assert_predicate(e, :private_call?)
  end

  def test_name_error_info_parent_iseq_mark
    assert_separately(['-', File.join(__dir__, 'bug-11928.rb')], <<-'end;')
      -> {require ARGV[0]}.call
    end;
  end

  def test_output_string_encoding
    # "\x82\xa0" in cp932 is "\u3042" (Japanese hiragana 'a')
    # change $stderr to force calling rb_io_write() instead of fwrite()
    assert_in_out_err(["-Eutf-8:cp932"], '# coding: cp932
$stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
      assert_equal 1, outs.size
      assert_equal 0, errs.size
      err = outs.first.force_encoding('utf-8')
      assert err.valid_encoding?, 'must be valid encoding'
      assert_match %r/\u3042/, err
    end
  end

  def test_multibyte_and_newline
    bug10727 = '[ruby-core:67473] [Bug #10727]'
    assert_in_out_err([], <<-'end;', [], /\u{306b 307b 3093 3054} \(E\)\n\u{6539 884c}/, bug10727, encoding: "UTF-8")
      class E < StandardError
        def initialize
          super("\u{306b 307b 3093 3054}\n\u{6539 884c}")
        end
      end
      raise E
    end;
  end

  def test_method_missing_reason_clear
    bug10969 = '[ruby-core:68515] [Bug #10969]'
    a = Class.new {def method_missing(*) super end}.new
    assert_raise(NameError) {a.instance_eval("foo")}
    assert_raise(NoMethodError, bug10969) {a.public_send("bar", true)}
  end

  def test_message_of_name_error
    assert_raise_with_message(NameError, /\Aundefined method `foo' for module `#<Module:.*>'$/) do
      Module.new do
        module_function :foo
      end
    end
  end

  def capture_warning_warn
    verbose = $VERBOSE
    warning = []

    ::Warning.class_eval do
      alias_method :warn2, :warn
      remove_method :warn

      define_method(:warn) do |str|
        warning << str
      end
    end

    $VERBOSE = true
    yield

    return warning
  ensure
    $VERBOSE = verbose

    ::Warning.class_eval do
      remove_method :warn
      alias_method :warn, :warn2
      remove_method :warn2
    end
  end

  def test_warning_warn
    warning = capture_warning_warn {@a}
    assert_match(/instance variable @a not initialized/, warning[0])

    assert_equal(["a\nz\n"], capture_warning_warn {warn "a\n", "z"})
    assert_equal([],         capture_warning_warn {warn})
    assert_equal(["\n"],     capture_warning_warn {warn ""})
  end

  def test_warning_warn_invalid_argument
    assert_raise(TypeError) do
      ::Warning.warn nil
    end
    assert_raise(TypeError) do
      ::Warning.warn 1
    end
    assert_raise(Encoding::CompatibilityError) do
      ::Warning.warn "\x00a\x00b\x00c".force_encoding("utf-16be")
    end
  end

  def test_warning_warn_circular_require_backtrace
    warning = nil
    path = nil
    Tempfile.create(%w[circular .rb]) do |t|
      path = File.realpath(t.path)
      basename = File.basename(path)
      t.puts "require '#{basename}'"
      t.close
      $LOAD_PATH.push(File.dirname(t))
      warning = capture_warning_warn {require basename}
    ensure
      $LOAD_PATH.pop
      $LOADED_FEATURES.delete(t)
    end
    assert_equal(1, warning.size)
    assert_match(/circular require/, warning.first)
    assert_match(/^\tfrom #{Regexp.escape(path)}:1:/, warning.first)
  end

  def test_warning_warn_super
    assert_in_out_err(%[-W0], "#{<<~"{#"}\n#{<<~'};'}", [], /instance variable @a not initialized/)
    {#
      module Warning
        def warn(message)
          super
        end
      end

      $VERBOSE = true
      @a
    };
  end

  def test_undefined_backtrace
    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
    begin;
      class Exception
        undef backtrace
      end

      assert_raise(RuntimeError) {
        raise RuntimeError, "hello"
      }
    end;
  end

  def test_redefined_backtrace
    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
    begin;
      $exc = nil

      class Exception
        undef backtrace
        def backtrace
          $exc = self
        end
      end

      e = assert_raise(RuntimeError) {
        raise RuntimeError, "hello"
      }
      assert_same(e, $exc)
    end;
  end

  def test_wrong_backtrace
    assert_separately([], "#{<<-"begin;"}\n#{<<-"end;"}")
    begin;
      class Exception
        undef backtrace
        def backtrace(a)
        end
      end

      assert_raise(RuntimeError) {
        raise RuntimeError, "hello"
      }
    end;
  end
end