This gem provides two new minitest assertions, assert_mail and refute_mail for easily testing whether a specific email has been sent by your application.

Add this line to your application's Gemfile:

gem 'mail_assertions'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mail_assertions

You need to include the module MailAssertions in ActiveSupport::TestCase.

Also, you almost certainly want to empty the deliveries list between every test (otherwise it's hard to know which emails came from this test).

Therefore, in your test_helper.rb:

class ActiveSupport::TestCase
  include MailAssertions

  def setup
    ActionMailer::Base.deliveries.clear
  end
end

Conditions is a hash of attributes on the message object and the value you're looking for.

# Fails unless there was exactly email sent with the subject
# Hello World
assert_mail subject: 'Hello World'

You can also specify several conditions, in which case all must apply for the email to match:

# Fails unless there was exactly one email with the subject Hello World
# sent to hello@example.com.
assert_mail subject: 'Hello World', to: ['hello@example.com']

Optionally, the values may be regular expressions in which case the email's value will need to match it

# Fails unless there was exactly one email with a subject starting
# with an A
assert_mail subject: /^A/

The optional block is invoked with the matching mail

assert_mail subject: 'Hello World' do |mail|
  # Further assertions about the email here
end

As a convenience, if the block accepts two arguments, the second will be the HTML body of the email (mail.html_part.body.to_s)

assert_mail subject: 'Hello World' do |mail, html|
  # Further assertions about the email or its html here
end

Works similarly to assert_mail but fails unless no emails matching the conditions have been sent.

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/hult/mail_assertions.

The gem is available as open source under the terms of the MIT License.