1 files changed, 22 insertions, 0 deletions
diff --git a/activemodel/test/cases/type/immutable_string_test.rb b/activemodel/test/cases/type/immutable_string_test.rb
new file mode 100644
index 0000000000..751f753ddb
--- /dev/null
+++ b/activemodel/test/cases/type/immutable_string_test.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+
+module ActiveModel
+  module Type
+    class ImmutableStringTest < ActiveModel::TestCase
+      test "cast strings are frozen" do
+        s = "foo"
+        type = Type::ImmutableString.new
+        assert_equal true, type.cast(s).frozen?
+      end
+
+      test "immutable strings are not duped coming out" do
+        s = "foo"
+        type = Type::ImmutableString.new
+        assert_same s, type.cast(s)
+        assert_same s, type.deserialize(s)
+      end
+    end
+  end
+end