```ruby
require_relative '../../spec_helper'

describe "ObjectSpace._id2ref" do
  it "converts an object id to a reference to the object" do
    s = "I am a string"
    r = ObjectSpace._id2ref(s.object_id)
    r.should == s
  end

  it "retrieves an Integer by object_id" do
    f = 1
    r = ObjectSpace._id2ref(f.object_id)
    r.should == f
  end

  it "retrieves a Symbol by object_id" do
    s = :sym
    r = ObjectSpace._id2ref(s.object_id)
    r.should == s
  end

  it 'raises RangeError when an object could not be found' do
    proc { ObjectSpace._id2ref(1 << 60) }.should raise_error(RangeError)
  end
end
```

Cover more cases for ObjectSpace._id2ref
user
```ruby
require_relative '../../spec_helper'

describe "ObjectSpace._id2ref" do
  it "converts an object id to a reference to the object" do
    s = "I am a string"
    r = ObjectSpace._id2ref(s.object_id)
    r.should == s
  end

  it "retrieves true by object_id" do
    ObjectSpace._id2ref(true.object_id).should == true
  end

  it "retrieves false by object_id" do
    ObjectSpace._id2ref(false.object_id).should == false
  end

  it "retrieves nil by object_id" do
    ObjectSpace._id2ref(nil.object_id).should == nil
  end

  it "retrieves a small Integer by object_id" do
    ObjectSpace._id2ref(1.object_id).should == 1
    ObjectSpace._id2ref((-42).object_id).should == -42
  end

  it "retrieves a large Integer by object_id" do
    obj = 1 << 88
    ObjectSpace._id2ref(obj.object_id).should.equal?(obj)
  end

  it "retrieves a Symbol by object_id" do
    ObjectSpace._id2ref(:sym.object_id).should.equal?(:sym)
  end

  it "retrieves a String by object_id" do
    obj = "str"
    ObjectSpace._id2ref(obj.object_id).should.equal?(obj)
  end

  it "retrieves a frozen literal String by object_id" do
    ObjectSpace._id2ref("frozen string literal _id2ref".freeze.object_id).should.equal?("frozen string literal _id2ref".freeze)
  end

  it "retrieves an Encoding by object_id" do
    ObjectSpace._id2ref(Encoding::UTF_8.object_id).should.equal?(Encoding::UTF_8)
  end

  it 'raises RangeError when an object could not be found' do
    proc { ObjectSpace._id2ref(1 << 60) }.should raise_error(RangeError)
  end
end
```
assistant