Ruby Logger Mocking

ruby_logger_mocking.md

Ruby Logger Mocking

TL;DR Best Option

The following statement is generally the best overall for mocking:

let (:log) { instance_double(Logger).as_null_object }
# - Creates an instance double of Logger with interface validation
# - Converts it into a null object that absorbs any unexpected method calls

Ensures interface compliance with Logger while absorbing any unexpected method calls.

Interface validation in this context means that when you use instance_double(Logger), RSpec ensures that any methods you stub or call on the double exist on the actual Logger class. This helps catch errors where you might be using methods that don't exist on Logger, ensuring your test double accurately reflects the real object's interface.

Other Mocking Options

let (:log) { double.as_null_object }
# - Creates a generic test double without interface validation
# - Converts it into a null object

let (:log) { instance_double(Logger) }
# - Creates an instance double of Logger with interface validation
# - Does not absorb unexpected method calls (will raise an error if an undefined method is called)

let (:log) { double("Logger").as_null_object }
# - Creates a generic test double named "Logger" without interface validation
# - Converts it into a null object