Test for nil, people not likely to assign it false.

actionpack/test/dispatch/cookies_test.rb

@@ -899,8 +899,8 @@ def test_legacy_signed_cookie_is_treated_as_nil_by_encrypted_cookie_jar_if_tampe
     assert_nil @response.cookies["foo"]
   end
 
-  def test_use_authenticated_cookie_encryption_uses_legacy_hmac_aes_cbc_encrypiton
-    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = false
+  def test_use_authenticated_cookie_encryption_uses_legacy_hmac_aes_cbc_encryption_when_not_enabled
+    @request.env["action_dispatch.use_authenticated_cookie_encryption"] = nil
 
     key_generator = @request.env["action_dispatch.key_generator"]
     encrypted_cookie_salt = @request.env["action_dispatch.encrypted_cookie_salt"]