1 files changed, 71 insertions, 24 deletions
diff --git a/spec/ruby/core/class/subclasses_spec.rb b/spec/ruby/core/class/subclasses_spec.rb
index ddbcfb02c0..c3d7b07e12 100644
--- a/spec/ruby/core/class/subclasses_spec.rb
+++ b/spec/ruby/core/class/subclasses_spec.rb
@@ -1,38 +1,85 @@
 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
+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" do
-      parent = Class.new
-      child = Class.new(parent)
-      mod = Module.new
-      parent.include(mod)
+  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
+    assert_subclasses(parent, [child])
+  end
 
-    it "does not return singleton classes" do
-      a = Class.new
+  it "does not return included modules from the child" do
+    parent = Class.new
+    child = Class.new(parent)
+    mod = Module.new
+    parent.include(mod)
 
-      a_obj = a.new
-      def a_obj.force_singleton_class
-        42
-      end
+    assert_subclasses(parent, [child])
+  end
 
-      a.subclasses.should_not include(a_obj.singleton_class)
-    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 "has 1 entry per module or class" do
-      ModuleSpecs::Parent.subclasses.should == ModuleSpecs::Parent.subclasses.uniq
+  it "does not return singleton classes" do
+    a = Class.new
+
+    a_obj = a.new
+    def a_obj.force_singleton_class
+      42
     end
 
-    def assert_subclasses(mod,subclasses)
-      mod.subclasses.sort_by(&:inspect).should == subclasses.sort_by(&:inspect)
+    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.is_a?(Class) }
+  end
+
+  def assert_subclasses(mod,subclasses)
+    mod.subclasses.sort_by(&:inspect).should == subclasses.sort_by(&:inspect)
   end
 end