How to rspec mock ruby rails logger class

Question

Hi I and trying to rspec mock the following class:

    class Person
      def initialize(personid)
        Rails.logger.debug "Creating person with id #{personid}"
      end
    end

Using this:

require 'spec_helper'
  describe Person do
    describe "#initialize" do
      let(:rails_mock) { double("Rails").as_null_object }
      let(:logger_mock) { double("Rails.logger").as_null_object }

      it "logs a message" do
        rails_mock.stub(:logger).and_return(logger_mock)
        logger_mock.should_receive(:debug)
        Person.new "dummy"
      end
   end
end

and getting this message:

RSpec::Mocks::MockExpectationError: (Double "Rails.logger").debug(any args)
expected: 1 time
received: 0 times

Any help would be great!

apneadiving · Accepted Answer · 2011-11-23 22:26:14Z

8

I'd do:

Rails.stub_chain(:logger, :debug).and_return(logger_mock)

Don't forget do unstub at the end of your test:

Rails.unstub(:logger)

answered Nov 23, 2011 at 22:26

apneadiving

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1 Comment

tamouse Over a year ago

This does not work for me. I get undefined method 'stub_chain' for Rails:Module (NoMethodError)

Philippe Rathé · Accepted Answer · 2019-10-29 20:39:20Z

5

Here is an updated answer to this using partial double:

let(:personid) { 'dummy' }

before do
  allow(Rails.logger).to receive(:debug).and_return nil
  Person.new(personid)
end

it { expect(Rails.logger).to have_received(:debug).with(a_string_matching(personid)) }

No need to "unstub" anything, RSpec does it for you.

answered Oct 29, 2019 at 20:39

Philippe Rathé

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Comments

lulalala · Accepted Answer · 2013-06-10 08:51:04Z

1

The stub did not work because those stubs aren't linked to the real code. It should be like this instead:

require 'spec_helper'
  describe Person do
    describe "#initialize" do
      let(:logger_mock) { double("Rails.logger").as_null_object }

      it "logs a message" do
        Rails.stub(:logger).and_return(logger_mock)
        logger_mock.should_receive(:debug)
        Person.new "dummy"
      end
   end
end

For OP: if you just want to set expectation on logging, you don't need to stub the whole logger class at all. You can just do

Rails.logger.should_receive(:debug)

Bonus: if you just want to stub so no logging will occur, do this:

Rails.logger.stub(:add){ true }

answered Jun 10, 2013 at 8:51

lulalala

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