```ruby
require 'abstract_unit'
require 'active_support/core_ext/object/inclusion'

class InTest < ActiveSupport::TestCase
  def test_in_array
    assert 1.in?([1,2])
    assert !3.in?([1,2])
  end

  def test_in_hash
    h = { "a" => 100, "b" => 200 }
    assert "a".in?(h)
    assert !"z".in?(h)
  end

  def test_in_string
    assert "lo".in?("hello")
    assert !"ol".in?("hello")
    assert ?h.in?("hello")
  end

  def test_in_range
    assert 25.in?(1..50)
    assert !75.in?(1..50)
  end

  def test_in_set
    s = Set.new([1,2])
    assert 1.in?(s)
    assert !3.in?(s)
  end

  module A
  end
  class B
    include A
  end
  class C < B
  end

  def test_in_module
    assert A.in?(B)
    assert A.in?(C)
    assert !A.in?(A)
  end
  
  def test_no_method_catching
    assert_raise(ArgumentError) { 1.in?(1) }
  end
  
  def test_present_in
    assert_equal "stuff", "stuff".present_in(%w( lots of stuff ))
    assert_not "stuff".present_in(%w( lots of crap ))
  end
end
```

Use assert_nil instead as its clearer about what the return is expected to be
user
```ruby
require 'abstract_unit'
require 'active_support/core_ext/object/inclusion'

class InTest < ActiveSupport::TestCase
  def test_in_array
    assert 1.in?([1,2])
    assert !3.in?([1,2])
  end

  def test_in_hash
    h = { "a" => 100, "b" => 200 }
    assert "a".in?(h)
    assert !"z".in?(h)
  end

  def test_in_string
    assert "lo".in?("hello")
    assert !"ol".in?("hello")
    assert ?h.in?("hello")
  end

  def test_in_range
    assert 25.in?(1..50)
    assert !75.in?(1..50)
  end

  def test_in_set
    s = Set.new([1,2])
    assert 1.in?(s)
    assert !3.in?(s)
  end

  module A
  end
  class B
    include A
  end
  class C < B
  end

  def test_in_module
    assert A.in?(B)
    assert A.in?(C)
    assert !A.in?(A)
  end
  
  def test_no_method_catching
    assert_raise(ArgumentError) { 1.in?(1) }
  end
  
  def test_present_in
    assert_equal "stuff", "stuff".present_in(%w( lots of stuff ))
    assert_nil "stuff".present_in(%w( lots of crap ))
  end
end
```
assistant