2 files changed, 38 insertions, 4 deletions
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index b67201d94d..8e5723c8e5 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -542,9 +542,6 @@ class AttributeMethodsTest < ActiveRecord::TestCase
 
     developer.save!
 
-    assert_equal "50000", developer.salary_before_type_cast
-    assert_equal 1337, developer.name_before_type_cast
-
     assert_equal 50000, developer.salary
     assert_equal "1337", developer.name
   end
diff --git a/activerecord/test/cases/attribute_test.rb b/activerecord/test/cases/attribute_test.rb
index 0f216b7a13..a24a4fc6a4 100644
--- a/activerecord/test/cases/attribute_test.rb
+++ b/activerecord/test/cases/attribute_test.rb
@@ -182,12 +182,49 @@ module ActiveRecord
       assert attribute.has_been_read?
     end
 
+    test "an attribute is not changed if it hasn't been assigned or mutated" do
+      attribute = Attribute.from_database(:foo, 1, Type::Value.new)
+
+      refute attribute.changed?
+    end
+
+    test "an attribute is changed if it's been assigned a new value" do
+      attribute = Attribute.from_database(:foo, 1, Type::Value.new)
+      changed = attribute.with_value_from_user(2)
+
+      assert changed.changed?
+    end
+
+    test "an attribute is not changed if it's assigned the same value" do
+      attribute = Attribute.from_database(:foo, 1, Type::Value.new)
+      unchanged = attribute.with_value_from_user(1)
+
+      refute unchanged.changed?
+    end
+
     test "an attribute can not be mutated if it has not been read,
       and skips expensive calculations" do
       type_which_raises_from_all_methods = Object.new
       attribute = Attribute.from_database(:foo, "bar", type_which_raises_from_all_methods)
 
-      assert_not attribute.changed_in_place_from?("bar")
+      assert_not attribute.changed_in_place?
+    end
+
+    test "an attribute is changed if it has been mutated" do
+      attribute = Attribute.from_database(:foo, "bar", Type::String.new)
+      attribute.value << "!"
+
+      assert attribute.changed_in_place?
+      assert attribute.changed?
+    end
+
+    test "an attribute can forget its changes" do
+      attribute = Attribute.from_database(:foo, "bar", Type::String.new)
+      changed = attribute.with_value_from_user("foo")
+      forgotten = changed.forgetting_assignment
+
+      assert changed.changed? # sanity check
+      refute forgotten.changed?
     end
 
     test "with_value_from_user validates the value" do