assert('Object#instance_exec') do class KlassWithSecret def initialize @secret = 99 end end k = KlassWithSecret.new assert_equal 104, k.instance_exec(5) {|x| @secret+x } end assert('Object#tap') do ret = [] (1..10) .tap {|x| ret << "original: #{x.inspect}"} .to_a .tap {|x| ret << "array: #{x.inspect}"} .select {|x| x%2==0} .tap {|x| ret << "evens: #{x.inspect}"} .map { |x| x*x } .tap {|x| ret << "squares: #{x.inspect}"} assert_equal [ "original: 1..10", "array: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]", "evens: [2, 4, 6, 8, 10]", "squares: [4, 16, 36, 64, 100]" ], ret assert_equal(:tap_ok, Class.new {def m; tap{return :tap_ok}; end}.new.m) end assert('instance_exec on primitives with class and module definition') do begin class A 1.instance_exec do class B end end end assert_kind_of Class, A::B ensure Object.remove_const :A end begin class A 1.instance_exec do module B end end end assert_kind_of Module, A::B ensure Object.remove_const :A end end