diff --git a/test/test_singleton.rb b/test/test_singleton.rb
index bd11095..259f9c5 100644
--- a/test/test_singleton.rb
+++ b/test/test_singleton.rb
@@ -2,14 +2,102 @@ require 'test/unit'
 require 'singleton'
 
 class TestSingleton < Test::Unit::TestCase
-  class C
+  class SingletonTest
     include Singleton
   end
 
   def test_marshal
-    o1 = C.instance
+    o1 = SingletonTest.instance
     m = Marshal.dump(o1)
     o2 = Marshal.load(m)
     assert_same(o1, o2)
   end
+
+  def test_instance_never_changes
+    a = SingletonTest.instance
+    b = SingletonTest.instance
+    assert_same a, b
+  end
+
+  def test_initialize_raises_exception
+    assert_raises NoMethodError do
+      SingletonTest.new
+    end
+  end
+
+  def test_allocate_raises_exception
+    assert_raises NoMethodError do
+      SingletonTest.allocate
+    end
+  end
+
+  def test_clone_raises_exception
+    exception = assert_raises TypeError do
+      SingletonTest.instance.clone
+    end
+
+    expected = "can't clone instance of singleton TestSingleton::SingletonTest"
+
+    assert_equal expected, exception.message
+  end
+
+  def test_dup_raises_exception
+    exception = assert_raises TypeError do
+      SingletonTest.instance.dup
+    end
+
+    expected = "can't dup instance of singleton TestSingleton::SingletonTest"
+
+    assert_equal expected, exception.message
+  end
+
+  def test_include_in_module_raises_exception
+    mod = Module.new
+
+    exception = assert_raises TypeError do
+      mod.class_eval do
+        include Singleton
+      end
+    end
+
+    expected = "Inclusion of the OO-Singleton module in module #{mod}"
+
+    assert_equal expected, exception.message
+  end
+
+  def test_extending_singleton_raises_exception
+    assert_raises NoMethodError do
+      'foo'.extend Singleton
+    end
+  end
+
+  def test_inheritance_works_with_overridden_inherited_method
+    super_super_called = false
+
+    outer = Class.new do
+      define_singleton_method :inherited do |sub|
+        super_super_called = true
+      end
+    end
+
+    inner = Class.new(outer) do
+      include Singleton
+    end
+
+    tester = Class.new(inner)
+
+    assert super_super_called
+
+    a = tester.instance
+    b = tester.instance
+    assert_same a, b
+  end
+
+  def test_class_level_cloning_preserves_singleton_behavior
+    klass = SingletonTest.clone
+
+    a = klass.instance
+    b = klass.instance
+    assert_same a, b
+  end
 end