diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index d5c1aaca12..a219bbdfa3 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -176,12 +176,12 @@ module ActionController
 
   # Methods #destroy and #load! are overridden to avoid calling methods on the
   # @store object, which does not exist for the TestSession class.
-  class TestSession < Rack::Session::Abstract::SessionHash #:nodoc:
+  class TestSession < Rack::Session::Abstract::PersistedSecure::SecureSessionHash #:nodoc:
     DEFAULT_OPTIONS = Rack::Session::Abstract::Persisted::DEFAULT_OPTIONS
 
     def initialize(session = {})
       super(nil, nil)
-      @id = SecureRandom.hex(16)
+      @id = Rack::Session::SessionId.new(SecureRandom.hex(16))
       @data = stringify_keys(session)
       @loaded = true
     end
diff --git a/actionpack/test/dispatch/session/test_session_test.rb b/actionpack/test/dispatch/session/test_session_test.rb
index 2d36990250..f3b1452d63 100644
--- a/actionpack/test/dispatch/session/test_session_test.rb
+++ b/actionpack/test/dispatch/session/test_session_test.rb
@@ -68,4 +68,10 @@ class ActionController::TestSessionTest < ActiveSupport::TestCase
     session = ActionController::TestSession.new(one: "1")
     assert_equal(2, session.fetch("2") { |key| key.to_i })
   end
+
+  def test_session_id
+    session = ActionController::TestSession.new
+    assert_instance_of String, session.id.public_id
+    assert_equal(session.id.public_id, session["session_id"])
+  end
 end