You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test_yaml_tree.rb
    path of file: ./repos/psych/test/psych/visitors
    
    the code of the file until where you have to start completion: # frozen_string_literal: true
require 'psych/helper'
require 'delegate'

module Psych
  module Visitors
    class TestYAMLTree < TestCase
      class TestDelegatorClass < Delegator
        def initialize(obj); super; @obj = obj; end
        def __setobj__(obj); @obj = obj; end
        def __getobj__; @obj if defined?(@obj); end
      end

      class TestSimpleDelegatorClass < SimpleDelegator
      end

      def setup
        super
        @v = Visitors::YAMLTree.create
      end

      def test_tree_can_be_called_twice
        @v.start
        @v << Object.new
        t = @v.tree
        assert_equal t, @v.tree
      end

      def test_yaml_tree_can_take_an_emitter
        io = StringIO.new
        e  = Psych::Emitter.new io
        v = Visitors::YAMLTree.create({}, e)
        v.start
        v << "hello world"
        v.finish

        assert_include io.string, "hello world"
      end

      def test_binary_formatting
        gif = "GIF89a\f\x00\f\x00\x84\x00\x00\xFF\xFF\xF7\xF5\xF5\xEE\xE9\xE9\xE5fff\x00\x00\x00\xE7\xE7\xE7^^^\xF3\xF3\xED\x8E\x8E\x8E\xE0\xE0\xE0\x9F\x9F\x9F\x93\x93\x93\xA7\xA7\xA7\x9E\x9E\x9Eiiiccc\xA3\xA3\xA3\x84\x84\x84\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9!\xFE\x0EMade with GIMP\x00,\x00\x00\x00\x00\f\x00\f\x00\x00\x05,  \x8E\x810\x9E\xE3@\x14\xE8i\x10\xC4\xD1\x8A\b\x1C\xCF\x80M$z\xEF\xFF0\x85p\xB8\xB01f\r\e\xCE\x01\xC3\x01\x1E\x10' \x82\n\x01\x00;".b
        @v << gif
        scalar = @v.tree.children.first.children.first
        assert_equal Psych::Nodes::Scalar::LITERAL, scalar.style
      end

      def test_object_has_no_class
        yaml = Psych.dump(Object.new)
        assert(Psych.dump(Object.new) !~ /Object/, yaml)
      end

      def test_struct_const
        foo = Struct.new("Foo", :bar)
        assert_cycle foo.new('bar')
        Struct.instance_eval { remove_const(:Foo) }
      end

      A = Struct.new(:foo)

      def test_struct
        assert_cycle A.new('bar')
      end

      def test_struct_anon
        s = Struct.new(:foo).new('bar')
        obj =  Psych.unsafe_load(Psych.dump(s))
        assert_equal s.foo, obj.foo
      end

      def test_override_method
        s = Struct.new(:method).new('override')
        obj =  Psych.unsafe_load(Psych.dump(s))
        assert_equal s.method, obj.method
      end

      def test_exception
        ex = Exception.new 'foo'
        loaded = Psych.unsafe_load(Psych.dump(ex))

        assert_equal ex.message, loaded.message
        assert_equal ex.class, loaded.class
      end

      def test_regexp
        assert_cycle(/foo/)
        assert_cycle(/foo/i)
        assert_cycle(/foo/mx)
      end

      def test_time
        t = Time.now
        assert_equal t, Psych.unsafe_load(Psych.dump(t))
      end

      def test_date
        date = Date.strptime('2002-12-14', '%Y-%m-%d')
        assert_cycle date
      end

      def test_rational
        assert_cycle Rational(1,2)
      end

      def test_complex
        assert_cycle Complex(1,2)
      end

      def test_scalar
        assert_cycle 'foo'
        assert_cycle ':foo'
        assert_cycle ''
        assert_cycle ':'
      end

      def test_boolean
        assert_cycle true
        assert_cycle 'true'
        assert_cycle false
        assert_cycle 'false'
      end

      def test_range_inclusive
        assert_cycle 1..2
      end

      def test_range_exclusive
        assert_cycle 1...2
      end

      def test_anon_class
        assert_raise(TypeError) do
          @v.accept Class.new
        end

        assert_raise(TypeError) do
          Psych.dump(Class.new)
        end
      end

      def test_hash
        assert_cycle('a' => 'b')
      end

      def test_list
        assert_cycle(%w{ a b })
        assert_cycle([1, 2.2])
      end

      def test_symbol
        assert_cycle :foo
      end

      def test_int
        assert_cycle 1
        assert_cycle(-1)
        assert_cycle '1'
        assert_cycle '-1'
      end

      def test_float
        assert_cycle 1.2
        assert_cycle '1.2'

        assert Psych.load(Psych.dump(0.0 / 0.0)).nan?
        assert_equal 1, Psych.load(Psych.dump(1 / 0.0)).infinite?
        assert_equal(-1, Psych.load(Psych.dump(-1 / 0.0)).infinite?)
      end

      def test_string
        assert_include(Psych.dump({'a' => '017'}), "'017'")
        assert_include(Psych.dump({'a' => '019'}), "'019'")
        assert_include(Psych.dump({'a' => '01818'}), "'01818'")
      end

      # http://yaml.org/type/null.html
      def test_nil
        assert_cycle nil
        assert_nil Psych.load('null')
        assert_nil Psych.load('Null')
       
    
        def initialize(obj); super; @obj = obj; end
        def __setobj__(obj); @obj = obj; end
        def __getobj__; @obj if defined?(@obj); end
      end

      class TestSimpleDelegatorClass < SimpleDelegator
      end

      def setup
        super
        @v = Visitors::YAMLTree.create
      end

      def test_tree_can_be_called_twice
        @v.start
        @v << Object.new
        t = @v.tree
        assert_equal t, @v.tree
      end

      def test_yaml_tree_can_take_an_emitter
        io = StringIO.new
        e  = Psych::Emitter.new io
        v = Visitors::YAMLTree.create({}, e)
        v.start
        v << "hello world"
        v.finish

        assert_include io.string, "hello world"
      end

      def test_binary_formatting
        gif = "GIF89a\f\x00\f\x00\x84\x00\x00\xFF\xFF\xF7\xF5\xF5\xEE\xE9\xE9\xE5fff\x00\x00\x00\xE7\xE7\xE7^^^\xF3\xF3\xED\x8E\x8E\x8E\xE0\xE0\xE0\x9F\x9F\x9F\x93\x93\x93\xA7\xA7\xA7\x9E\x9E\x9Eiiiccc\xA3\xA3\xA3\x84\x84\x84\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9\xFF\xFE\xF9!\xFE\x0EMade with GIMP\x00,\x00\x00\x00\x00\f\x00\f\x00\x00\x05,  \x8E\x810\x9E\xE3@\x14\xE8i\x10\xC4\xD1\x8A\b\x1C\xCF\x80M$z\xEF\xFF0\x85p\xB8\xB01f\r\e\xCE\x01\xC3\x01\x1E\x10' \x82\n\x01\x00;".b
        @v << gif
        scalar = @v.tree.children.first.children.first
        assert_equal Psych::Nodes::Scalar::LITERAL, scalar.style
      end

      def test_object_has_no_class
        yaml = Psych.dump(Object.new)
        assert(Psych.dump(Object.new) !~ /Object/, yaml)
      end

      def test_struct_const
        foo = Struct.new("Foo", :bar)
        assert_cycle foo.new('bar')
        Struct.instance_eval { remove_const(:Foo) }
      end

      A = Struct.new(:foo)

      def test_struct
        assert_cycle A.new('bar')
      end

      def test_struct_anon
        s = Struct.new(:foo).new('bar')
        obj =  Psych.unsafe_load(Psych.dump(s))
        assert_equal s.foo, obj.foo
      end

      def test_override_method
        s = Struct.new(:method).new('override')
        obj =  Psych.unsafe_load(Psych.dump(s))
        assert_equal s.method, obj.method
      end

      def test_exception
        ex = Exception.new 'foo'
        loaded = Psych.unsafe_load(Psych.dump(ex))

        assert_equal ex.message, loaded.message
        assert_equal ex.class, loaded.class
      end

      def test_regexp
        assert_cycle(/foo/)
        assert_cycle(/foo/i)
        assert_cycle(/foo/mx)
      end

      def test_time
        t = Time.now
        assert_equal t, Psych.unsafe_load(Psych.dump(t))
      end

      def test_date
        date = Date.strptime('2002-12-14', '%Y-%m-%d')
        assert_cycle date
      end

      def test_rational
        assert_cycle Rational(1,2)
      end

      def test_complex
        assert_cycle Complex(1,2)
      end

      def test_scalar
        assert_cycle 'foo'
        assert_cycle ':foo'
        assert_cycle ''
        assert_cycle ':'
      end

      def test_boolean
        assert_cycle true
        assert_cycle 'true'
        assert_cycle false
        assert_cycle 'false'
      end

      def test_range_inclusive
        assert_cycle 1..2
      end

      def test_range_exclusive
        assert_cycle 1...2
      end

      def test_anon_class
        assert_raise(TypeError) do
          @v.accept Class.new
        end

        assert_raise(TypeError) do
          Psych.dump(Class.new)
        end
      end

      def test_hash
        assert_cycle('a' => 'b')
      end

      def test_list
        assert_cycle(%w{ a b })
        assert_cycle([1, 2.2])
      end

      def test_symbol
        assert_cycle :foo
      end

      def test_int
        assert_cycle 1
        assert_cycle(-1)
        assert_cycle '1'
        assert_cycle '-1'
      end

      def test_float
        assert_cycle 1.2
        assert_cycle '1.2'

        assert Psych.load(Psych.dump(0.0 / 0.0)).nan?
        assert_equal 1, Psych.load(Psych.dump(1 / 0.0)).infinite?
        assert_equal(-1, Psych.load(Psych.dump(-1 / 0.0)).infinite?)
      end

      def test_string
        assert_include(Psych.dump({'a' => '017'}), "'017'")
        assert_include(Psych.dump({'a' => '019'}), "'019'")
        assert_include(Psych.dump({'a' => '01818'}), "'01818'")
      end

      # http://yaml.org/type/null.html
      def test_nil
        assert_cycle nil
        assert_nil Psych.load('null')
        assert_nil Psych.load('Null')
        assert_nil Psych.load('NULL')
        assert_nil Psych.load('~')
        assert_equal({'foo' => nil}, Psych.load('foo: '))

        assert_cycle 'null'
        assert_cycle 'nUll'
        assert_cycle '~'
      end

      def test_delegator
        assert_cycle(TestDelegatorClass.new([1, 2, 3]))
      end

      def test_simple_delegator
        assert_cycle(TestSimpleDelegatorClass.new([1, 2, 3]))
      end
    end