RSpec: how to test Rails logger message expectations?

Question

I am trying to test that the Rails logger receives messages in some of my specs. I am using the Logging gem.

Let\'s say that I have a class like this:

Answer 1

While I agree you generally don't want to test loggers, there are times it may be useful.

I have had success with expectations on Rails.logger.

Using RSpec's deprecated should syntax:

Rails.logger.should_receive(:info).with("some message")

Using RSpec's newer expect syntax:

expect(Rails.logger).to receive(:info).with("some message")

Note: In controller and model specs, you have to put this line before the message is logged. If you put it after, you'll get an error message like this:

Failure/Error: expect(Rails.logger).to receive(:info).with("some message")
       (#).info("some message")
           expected: 1 time with arguments: ("some message")
           received: 0 times