Add missing test cases for #assert_no_difference

1 files changed, 19 insertions, 1 deletions

diff --git a/activesupport/test/test_test.rb b/activesupport/test/test_test.rb
index 0fa08c0e3a..6f63a8a725 100644
--- a/activesupport/test/test_test.rb
+++ b/activesupport/test/test_test.rb
@@ -28,12 +28,30 @@ class AssertDifferenceTest < ActiveSupport::TestCase
     assert_equal 'custom', e.message
   end
 
-  def test_assert_no_difference
+  def test_assert_no_difference_pass
     assert_no_difference '@object.num' do
       # ...
     end
   end
 
+  def test_assert_no_difference_fail
+    error = assert_raises(Minitest::Assertion) do
+      assert_no_difference '@object.num' do
+        @object.increment
+      end
+    end
+    assert_equal "\"@object.num\" didn't change by 0.\nExpected: 0\n  Actual: 1", error.message
+  end
+
+  def test_assert_no_difference_with_message_fail
+    error = assert_raises(Minitest::Assertion) do
+      assert_no_difference '@object.num', 'Object Changed' do
+        @object.increment
+      end
+    end
+    assert_equal "Object Changed.\n\"@object.num\" didn't change by 0.\nExpected: 0\n  Actual: 1", error.message
+  end
+
   def test_assert_difference
     assert_difference '@object.num', +1 do
       @object.increment