How to test a mailer that has a date with accents?

In my mailer I have a date with Spanish format:

sbado, 21 de julio del 2012

I have a custom formatter for that configured in my
config/locales/es.yml

my_date_format: ! ‘%A, %-d de %B del %Y, %k:%M’

I’m trying to test it this way:

test “date with accent” do
mail = MyMailer.my_template

assert_match I18n.l(@object.date, format: :my_date_format),
mail.body.encoded
end

But it fails:

Running tests:

F

Finished tests in 0.438078s, 2.2827 tests/s, 15.9789 assertions/s.

  1. Failure: test_date_with_accent(MyMailerTest)
    [test/unit/mailers/my_mailer_test.rb:12]: Expected /sbado,\ 21\ de\
    julio
    del\ 2012,\ 14:10/ to match “… …s=C3=A1bado, 21 de julio del
    2012, 14:10\r\n …”.

(I have omitted the rest of the email content)