As of Ruby v2.2, nil is frozen so these tests are irrelevant.

In all these scenarios in the latest versions of Ruby, a `Mocha::StubbingError`
will be raised with the message: "can't stub method on frozen object: nil".

This behaviour is already tested in the more generic `StubbingFrozenObjectTest`
and so it's safe to ignore these tests for the relevant versions of Ruby.

test/acceptance/stubbing_nil_test.rb

@@ -13,47 +13,49 @@ def teardown
     teardown_acceptance_test
   end
 
-  def test_should_allow_stubbing_method_on_nil
-    Mocha::Configuration.allow(:stubbing_method_on_nil)
-    test_result = run_as_test do
-      nil.stubs(:stubbed_method)
+  if RUBY_VERSION < '2.2.0'
+    def test_should_allow_stubbing_method_on_nil
+      Mocha::Configuration.allow(:stubbing_method_on_nil)
+      test_result = run_as_test do
+        nil.stubs(:stubbed_method)
+      end
+      assert_passed(test_result)
+      assert !@logger.warnings.include?("stubbing method on nil: nil.stubbed_method")
     end
-    assert_passed(test_result)
-    assert !@logger.warnings.include?("stubbing method on nil: nil.stubbed_method")
-  end
 
-  def test_should_warn_on_stubbing_method_on_nil
-    Mocha::Configuration.warn_when(:stubbing_method_on_nil)
-    test_result = run_as_test do
-      nil.stubs(:stubbed_method)
+    def test_should_warn_on_stubbing_method_on_nil
+      Mocha::Configuration.warn_when(:stubbing_method_on_nil)
+      test_result = run_as_test do
+        nil.stubs(:stubbed_method)
+      end
+      assert_passed(test_result)
+      assert @logger.warnings.include?("stubbing method on nil: nil.stubbed_method")
     end
-    assert_passed(test_result)
-    assert @logger.warnings.include?("stubbing method on nil: nil.stubbed_method")
-  end
 
-  def test_should_prevent_stubbing_method_on_nil
-    Mocha::Configuration.prevent(:stubbing_method_on_nil)
-    test_result = run_as_test do
-      nil.stubs(:stubbed_method)
+    def test_should_prevent_stubbing_method_on_nil
+      Mocha::Configuration.prevent(:stubbing_method_on_nil)
+      test_result = run_as_test do
+        nil.stubs(:stubbed_method)
+      end
+      assert_failed(test_result)
+      assert test_result.error_messages.include?("Mocha::StubbingError: stubbing method on nil: nil.stubbed_method")
     end
-    assert_failed(test_result)
-    assert test_result.error_messages.include?("Mocha::StubbingError: stubbing method on nil: nil.stubbed_method")
-  end
 
-  def test_should_default_to_prevent_stubbing_method_on_non_mock_object
-    test_result = run_as_test do
-      nil.stubs(:stubbed_method)
+    def test_should_default_to_prevent_stubbing_method_on_non_mock_object
+      test_result = run_as_test do
+        nil.stubs(:stubbed_method)
+      end
+      assert_failed(test_result)
+      assert test_result.error_messages.include?("Mocha::StubbingError: stubbing method on nil: nil.stubbed_method")
     end
-    assert_failed(test_result)
-    assert test_result.error_messages.include?("Mocha::StubbingError: stubbing method on nil: nil.stubbed_method")
-  end
 
-  def test_should_allow_stubbing_method_on_non_nil_object
-    Mocha::Configuration.prevent(:stubbing_method_on_nil)
-    object = Object.new
-    test_result = run_as_test do
-      object.stubs(:stubbed_method)
+    def test_should_allow_stubbing_method_on_non_nil_object
+      Mocha::Configuration.prevent(:stubbing_method_on_nil)
+      object = Object.new
+      test_result = run_as_test do
+        object.stubs(:stubbed_method)
+      end
+      assert_passed(test_result)
     end
-    assert_passed(test_result)
   end
 end