Testing ActionMailer multipart emails(text and html version) with RSpec

To supplement, nilmethod’s excellent answer, you can clean up your specs by testing both text and html versions using a shared example group:

spec_helper.rb

def get_message_part (mail, content_type)
  mail.body.parts.find { |p| p.content_type.match content_type }.body.raw_source
end

shared_examples_for "multipart email" do
  it "generates a multipart message (plain text and html)" do
    mail.body.parts.length.should eq(2)
    mail.body.parts.collect(&:content_type).should == ["text/plain; charset=UTF-8", "text/html; charset=UTF-8"]
  end
end

your_email_spec.rb

let(:mail) { YourMailer.action }

shared_examples_for "your email content" do
  it "has some content" do
    part.should include("the content")
  end
end

it_behaves_like "multipart email"

describe "text version" do
  it_behaves_like "your email content" do
    let(:part) { get_message_part(mail, /plain/) }
  end
end

describe "html version" do
  it_behaves_like "your email content" do
    let(:part) { get_message_part(mail, /html/) }
  end
end