1 files changed, 50 insertions, 1 deletions
diff --git a/spec/ruby/core/class/subclasses_spec.rb b/spec/ruby/core/class/subclasses_spec.rb
index ddbcfb02c0..50eb5358d9 100644
--- a/spec/ruby/core/class/subclasses_spec.rb
+++ b/spec/ruby/core/class/subclasses_spec.rb
@@ -7,7 +7,7 @@ ruby_version_is '3.1' do
       assert_subclasses(ModuleSpecs::Parent, [ModuleSpecs::Child, ModuleSpecs::Child2])
     end
 
-    it "does not return included modules" do
+    it "does not return included modules from the parent" do
       parent = Class.new
       child = Class.new(parent)
       mod = Module.new
@@ -16,6 +16,33 @@ ruby_version_is '3.1' do
       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
 
@@ -31,6 +58,28 @@ ruby_version_is '3.1' 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