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Discussion on: RSpec: when to use double instead of instance_double

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robcodes profile image
RobCodes •

Could you explain a little more about the return here?

Later in the test, are you testing that the email has been delivered?

I believe that using a strict return double i.g. instance_double allows you to be more explicit with your return.

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vasily profile image
Vasily Polovnyov •

Later in the test, are you testing that the email has been delivered?

Not in this case. If I'd have to test that the email has been delivered, I'd assign it and verify:

last_deadline_warning_email = double(...) # or instance_double

allow(DeadlineMailer)
  .to receive(:last_deadline_warning)
  .and_return(last_deadline_warning_email)

# ...

expect(last_deadling_warning_email).to have_received(:deliver_later)
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In this particular case I simply stub emails in order to speed up tests. Consider the following example:

describe "#trigger_deadline_alerts" do
  it "..."
  it "..."
  it "..."
  it "..."
end
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Without stub we'd have to render and send deadline email 4 times which could be expensive and time consuming.