Test Action Mailer Content With Rspec Matchers In Rails
Mailers break quietly — a renamed method in a template, a missing interpolation, a recipient list that silently resolves to nil. None of it surfaces until a customer says they never got the email.
Description
Test the mailer directly rather than through a request. MyMailer.welcome(user) returns a Mail::Message you can assert on without delivering anything, and it runs in milliseconds.
Assert on the parts that matter: recipient, subject, and the specific content the template is responsible for producing. Both parts of a multipart email should be checked — HTML and text drift apart constantly because only one gets updated.
For the enqueue side, use have_enqueued_mail in the spec for the code that triggers it. That keeps the mailer spec about content and the caller’s spec about behaviour.
Sample input:
OrderMailer.confirmation(order)
Sample Output:
# mail.to => ["[email protected]"]
# mail.subject => "Your order ABC-1 is confirmed"
Answer
RSpec.describe OrderMailer, type: :mailer do
let(:user) { create(:user, email: "[email protected]", name: "Ada") }
let(:order) { create(:order, user: user, sku: "ABC-1", total_cents: 4250) }
describe "#confirmation" do
subject(:mail) { described_class.confirmation(order) }
it "addresses the order's user" do
expect(mail.to).to eq(["[email protected]"])
expect(mail.from).to eq(["[email protected]"])
end
it "names the SKU in the subject" do
expect(mail.subject).to eq("Your order ABC-1 is confirmed")
end
it "includes the total in both parts" do
html = mail.html_part.body.decoded
text = mail.text_part.body.decoded
expect(html).to include("42.50").and include("Ada")
expect(text).to include("42.50")
end
it "links to the order" do
expect(mail.html_part.body.decoded)
.to include(order_url(order, host: "example.com"))
end
end
end
# The enqueue side, tested where the behaviour lives
RSpec.describe CreateOrder do
it "enqueues the confirmation email" do
expect { described_class.new(user:, params:).call }
.to have_enqueued_mail(OrderMailer, :confirmation)
end
end
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