1 files changed, 92 insertions, 4 deletions
diff --git a/test/ruby/test_variable.rb b/test/ruby/test_variable.rb
index b053e11607..d425b43b0d 100644
--- a/test/ruby/test_variable.rb
+++ b/test/ruby/test_variable.rb
@@ -29,12 +29,39 @@ class TestVariable < Test::Unit::TestCase
     @@rule = "Cronus"			# modifies @@rule in Gods
     include Olympians
     def ruler4
-      EnvUtil.suppress_warning {
-        @@rule
-      }
+      @@rule
     end
   end
 
+  Athena = Gods.clone
+
+  def test_cloned_classes_copy_cvar_cache
+    assert_equal "Cronus", Athena.new.ruler0
+  end
+
+  def test_setting_class_variable_on_module_through_inheritance
+    mod = Module.new
+    mod.class_variable_set(:@@foo, 1)
+    mod.freeze
+    c = Class.new { include(mod) }
+    assert_raise(FrozenError) { c.class_variable_set(:@@foo, 2) }
+    assert_raise(FrozenError) { c.class_eval("@@foo = 2") }
+    assert_equal(1, c.class_variable_get(:@@foo))
+  end
+
+  Zeus = Gods.clone
+
+  def test_cloned_allows_setting_cvar
+    Zeus.class_variable_set(:@@rule, "Athena")
+
+    god = Gods.new.ruler0
+    zeus = Zeus.new.ruler0
+
+    assert_equal "Cronus", god
+    assert_equal "Athena", zeus
+    assert_not_equal god.object_id, zeus.object_id
+  end
+
   def test_singleton_class_included_class_variable
     c = Class.new
     c.extend(Olympians)
@@ -63,6 +90,67 @@ class TestVariable < Test::Unit::TestCase
     assert_equal(1, o.singleton_class.class_variable_get(:@@foo))
   end
 
+  def test_cvar_overtaken_by_parent_class
+    error = eval <<~EORB
+      class Parent
+      end
+
+      class Child < Parent
+        @@cvar = 1
+
+        def self.cvar
+          @@cvar
+        end
+      end
+
+      assert_equal 1, Child.cvar
+
+      class Parent
+        @@cvar = 2
+      end
+
+      assert_raise RuntimeError do
+        Child.cvar
+      end
+    EORB
+
+    assert_equal "class variable @@cvar of TestVariable::Child is overtaken by TestVariable::Parent", error.message
+  ensure
+    TestVariable.send(:remove_const, :Child) rescue nil
+    TestVariable.send(:remove_const, :Parent) rescue nil
+  end
+
+  def test_cvar_overtaken_by_module
+    error = eval <<~EORB
+      class ParentForModule
+        @@cvar = 1
+
+        def self.cvar
+          @@cvar
+        end
+      end
+
+      assert_equal 1, ParentForModule.cvar
+
+      module Mixin
+        @@cvar = 2
+      end
+
+      class ParentForModule
+        include Mixin
+      end
+
+      assert_raise RuntimeError do
+        ParentForModule.cvar
+      end
+    EORB
+
+    assert_equal "class variable @@cvar of TestVariable::ParentForModule is overtaken by TestVariable::Mixin", error.message
+  ensure
+    TestVariable.send(:remove_const, :Mixin) rescue nil
+    TestVariable.send(:remove_const, :ParentForModule) rescue nil
+  end
+
   class IncludeRefinedModuleClassVariableNoWarning
     module Mod
       @@_test_include_refined_module_class_variable = true
@@ -107,7 +195,7 @@ class TestVariable < Test::Unit::TestCase
     atlas = Titans.new
     assert_equal("Cronus", atlas.ruler0)
     assert_equal("Zeus", atlas.ruler3)
-    assert_equal("Cronus", atlas.ruler4)
+    assert_raise(RuntimeError) { atlas.ruler4 }
     assert_nothing_raised do
       class << Gods
         defined?(@@rule) && @@rule