Minitest or SimpleDelagator problem?

output

$ ruby q.rb 
1 true
2 false
3 true
4 false
5 A
Run options: --seed 65268

# Running tests:

FF

Finished tests in 0.001205s, 1659.7510 tests/s, 1659.7510 assertions/s.

  1) Failure:
test_0001_should_be_a_kind_of_a(X) [q.rb:21]:
Expected #<B:0x007fa9a9894ef0> to be a kind of A, not B.

  2) Failure:
test_0002_should_be_an_instance_of_a(X) [q.rb:24]:
Expected #<B:0x007fa9a9894ef0> to be an instance of A, not B.

2 tests, 2 assertions, 2 failures, 0 errors, 0 skips

q.rb

require 'delegate'
class A < SimpleDelegator
  def initialize(obj)
    super(obj)
  end
end
class B; end
x = A.new(B.new)
puts "1 #{x.kind_of?(A)}"
puts "2 #{x.kind_of?(B)}"

puts "3 #{x.instance_of?(A)}"
puts "4 #{x.instance_of?(B)}"

puts "5 #{x.class}"

require 'minitest/autorun'
require 'minitest/spec'
describe "X" do
  it "should be a kind of A" do
    x.must_be_kind_of(A)
  end
  it "should be an instance of A" do
    x.must_be_instance_of(A)
  end
end