4 files changed, 121 insertions, 38 deletions
diff --git a/spec/ruby/core/class/attached_object_spec.rb b/spec/ruby/core/class/attached_object_spec.rb
new file mode 100644
index 0000000000..f1c0f63a44
--- /dev/null
+++ b/spec/ruby/core/class/attached_object_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../spec_helper'
+
+ruby_version_is '3.2' do
+  describe "Class#attached_object" do
+    it "returns the object that is attached to a singleton class" do
+      a = Class.new
+
+      a_obj = a.new
+      a_obj.singleton_class.attached_object.should == a_obj
+    end
+
+    it "returns the class object that is attached to a class's singleton class" do
+      a = Class.new
+      singleton_class = (class << a; self; end)
+
+      singleton_class.attached_object.should == a
+    end
+
+    it "raises TypeError if the class is not a singleton class" do
+      a = Class.new
+
+      -> { a.attached_object }.should raise_error(TypeError, /is not a singleton class/)
+    end
+
+    it "raises TypeError for special singleton classes" do
+      -> { nil.singleton_class.attached_object }.should raise_error(TypeError, /[`']NilClass' is not a singleton class/)
+      -> { true.singleton_class.attached_object }.should raise_error(TypeError, /[`']TrueClass' is not a singleton class/)
+      -> { false.singleton_class.attached_object }.should raise_error(TypeError, /[`']FalseClass' is not a singleton class/)
+    end
+  end
+end
diff --git a/spec/ruby/core/class/descendants_spec.rb b/spec/ruby/core/class/descendants_spec.rb
deleted file mode 100644
index f87cd68be8..0000000000
--- a/spec/ruby/core/class/descendants_spec.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../module/fixtures/classes'
-
-ruby_version_is '3.1' do
-  describe "Class#descendants" do
-    it "returns a list of classes descended from self (excluding self)" do
-      assert_descendants(ModuleSpecs::Parent, [ModuleSpecs::Child, ModuleSpecs::Child2, ModuleSpecs::Grandchild])
-    end
-
-    it "does not return included modules" do
-      parent = Class.new
-      child = Class.new(parent)
-      mod = Module.new
-      parent.include(mod)
-
-      assert_descendants(parent, [child])
-    end
-
-    it "does not return singleton classes" do
-      a = Class.new
-
-      a_obj = a.new
-      def a_obj.force_singleton_class
-        42
-      end
-
-      a.descendants.should_not include(a_obj.singleton_class)
-    end
-
-    it "has 1 entry per module or class" do
-      ModuleSpecs::Parent.descendants.should == ModuleSpecs::Parent.descendants.uniq
-    end
-
-    def assert_descendants(mod, descendants)
-      mod.descendants.sort_by(&:inspect).should == descendants.sort_by(&:inspect)
-    end
-  end
-end
diff --git a/spec/ruby/core/class/dup_spec.rb b/spec/ruby/core/class/dup_spec.rb
index 701fd72e19..c09ed71b31 100644
--- a/spec/ruby/core/class/dup_spec.rb
+++ b/spec/ruby/core/class/dup_spec.rb
@@ -61,4 +61,7 @@ describe "Class#dup" do
     CoreClassSpecs::RecordCopy.name.should == "CoreClassSpecs::RecordCopy"
   end
 
+  it "raises TypeError if called on BasicObject" do
+    -> { BasicObject.dup }.should raise_error(TypeError, "can't copy the root class")
+  end
 end
diff --git a/spec/ruby/core/class/subclasses_spec.rb b/spec/ruby/core/class/subclasses_spec.rb
new file mode 100644
index 0000000000..50eb5358d9
--- /dev/null
+++ b/spec/ruby/core/class/subclasses_spec.rb
@@ -0,0 +1,87 @@
+require_relative '../../spec_helper'
+require_relative '../module/fixtures/classes'
+
+ruby_version_is '3.1' do
+  describe "Class#subclasses" do
+    it "returns a list of classes directly inheriting from self" do
+      assert_subclasses(ModuleSpecs::Parent, [ModuleSpecs::Child, ModuleSpecs::Child2])
+    end
+
+    it "does not return included modules from the parent" do
+      parent = Class.new
+      child = Class.new(parent)
+      mod = Module.new
+      parent.include(mod)
+
+      assert_subclasses(parent, [child])
+    end
+
+    it "does not return included modules from the child" do
+      parent = Class.new
+      child = Class.new(parent)
+      mod = Module.new
+      parent.include(mod)
+
+      assert_subclasses(parent, [child])
+    end
+
+    it "does not return prepended modules from the parent" do
+      parent = Class.new
+      child = Class.new(parent)
+      mod = Module.new
+      parent.prepend(mod)
+
+      assert_subclasses(parent, [child])
+    end
+
+    it "does not return prepended modules from the child" do
+      parent = Class.new
+      child = Class.new(parent)
+      mod = Module.new
+      child.prepend(mod)
+
+      assert_subclasses(parent, [child])
+    end
+
+    it "does not return singleton classes" do
+      a = Class.new
+
+      a_obj = a.new
+      def a_obj.force_singleton_class
+        42
+      end
+
+      a.subclasses.should_not include(a_obj.singleton_class)
+    end
+
+    it "has 1 entry per module or class" do
+      ModuleSpecs::Parent.subclasses.should == ModuleSpecs::Parent.subclasses.uniq
+    end
+
+    it "works when creating subclasses concurrently" do
+      t = 16
+      n = 1000
+      go = false
+      superclass = Class.new
+
+      threads = t.times.map do
+        Thread.new do
+          Thread.pass until go
+          n.times.map do
+            Class.new(superclass)
+          end
+        end
+      end
+
+      go = true
+      classes = threads.map(&:value)
+
+      superclass.subclasses.size.should == t * n
+      superclass.subclasses.each { |c| c.should be_kind_of(Class) }
+    end
+
+    def assert_subclasses(mod,subclasses)
+      mod.subclasses.sort_by(&:inspect).should == subclasses.sort_by(&:inspect)
+    end
+  end
+end