Rspec - How to replace receive by have_received when dealing with an expect within a block?

Question

I have the following Ruby class I want to test:

class Logger
  # ...

  def process
    X.process
  rescue StandardError => e
    ::Rails.logger.error('Progname') { 'Could not produce the audit log' }
    ::Rails.logger.error('Progname') { e.message }
    ::Rails.logger.error('Progname') { e.backtrace.join("\n") }
  end
end

And my RSpec test that currently works:

require 'spec_helper'

describe Logger do
  before do
    stub_const('Rails', double('Rails', logger: rails_logger))
  end

  let(:rails_logger) { instance_double(Logger, error: nil) }

  describe '#process' do
    subject(:process) { log.process }

    context 'when an exception occurs' do
      let(:error) do
        StandardError.new('Something went wrong')
      end

      before do
        allow(X).to receive(:process).and_raise(error)
        allow(error).to receive(:backtrace)
          .and_return(['backtrace:1', 'backtrace:2'])
      end

      it 'logs an error message' do
        expect(rails_logger).to(receive(:error).with('Progname')) do |&block|
          expect(block.call).to eq('Could not produce the audit log')
        end

        expect(rails_logger).to(receive(:error).with('Progname')) do |&block|
          expect(block.call).to eq('Something went wrong')
        end

        expect(rails_logger).to(receive(:error).with('Progname')) do |&block|
          expect(block.call).to eq("backtrace:1\nbacktrace:2")
        end

        process
      end
    end
  end
end

Now I want to use the have_received form instead so I changed my code to:

it 'logs an error message' do
  process

  expect(rails_logger).to(have_received(:error).with('Progname')) do |&block|
    expect(block.call).to eq('Could not produce the audit log')
  end

  expect(rails_logger).to(have_received(:error).with('Progname')) do |&block|
    expect(block.call).to eq('Something went wrong')
  end

  expect(rails_logger).to(have_received(:error).with('Progname')) do |&block|
    expect(block.call).to eq("backtrace:1\nbacktrace:2")
  end        
end

but the block evaluation fails:

Failure/Error: expect(block.call).to eq('Could not produce the audit log')
     
       expected: "Could not produce the audit log"
            got: "Something went wrong"

It seems the strategy of the block evaluation is different there and if the expect within the block fails, instead of trying another expectation it fails immediately. I don't know how to rewrite my existing code.

Thanks.

Rescuing StandardError in your logger isn't a very good idea as it will just make debugging more difficult. There are better alternatives for logging errors. — max
– max, Commented Feb 10 at 10:57

mochatiger · Accepted Answer · 2025-02-12 21:03:43Z

0

To simplify, instead of stubbing the logger with an instance, use allow:

before do
  allow(Rails.logger).to receive(:error)
end

Then your example becomes and passes:

it 'logs an error message' do
  yielded = []

  process

  expect(Rails.logger).to have_received(:error).with('Progname').thrice do |&block|
    yielded << block.call
  end
  expect(yielded).to eq ["Could not produce the audit log", "Something went wrong", "backtrace:1\nbacktrace:2"]
end

answered Feb 12 at 21:03

mochatiger

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1 Comment

Aymeric Feb 13 at 16:09

Thanks @mochatiger, it was indeed a solution I'd been considering but that's a little "out of the box" with a manual instrumentation. I was hoping a more native solution without extra work. Maybe I could create an issue on rspec, because I don't know why there is no have_received solution here.

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