ruby - Suppress console output during RSpec tests

Question

I am testing the class which put on the console some messages (with puts, p warnings and etc.). I am just wondering if there is any ability to suppress this output during RSpec tests ?

Answer 1

I suppress puts output in my classes by redirecting $stout to a text file. That way, if I need to see the output for any reason, it is there but it doesn't muddy up my test results.

#spec_helper.rb
RSpec.configure do |config|
  config.before(:all, &:silence_output)
  config.after(:all,  &:enable_output)
end

public
# Redirects stderr and stout to /dev/null.txt
def silence_output
  # Store the original stderr and stdout in order to restore them later
  @original_stderr = $stderr
  @original_stdout = $stdout

  # Redirect stderr and stdout
  $stderr = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
  $stdout = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
end

# Replace stderr and stdout so anything else is output correctly
def enable_output
  $stderr = @original_stderr
  $stdout = @original_stdout
  @original_stderr = nil
  @original_stdout = nil
end

EDIT:

In response to the comment by @MyronMarston, it probably would be smarter to just insert the methods directly into before and after as blocks.

#spec_helper.rb
RSpec.configure do |config|
  original_stderr = $stderr
  original_stdout = $stdout
  config.before(:all) do 
    # Redirect stderr and stdout
    $stderr = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
    $stdout = File.new(File.join(File.dirname(__FILE__), 'dev', 'null.txt'), 'w')
  end
  config.after(:all) do 
    $stderr = original_stderr
    $stdout = original_stdout
  end
end

It looks a little cleaner and keeps methods off of main. Also, note that if you are using Ruby 2.0, you can use __dir__ instead of File.dirname(__FILE__).

EDIT2

Also it should be mentioned, that you can forward to true os /dev/null by using File::NULL as it was introduced in Ruby v 1.9.3. (jruby 1.7)

Then the code snippet will look as following:

#spec_helper.rb
RSpec.configure do |config|
  original_stderr = $stderr
  original_stdout = $stdout
  config.before(:all) do
    # Redirect stderr and stdout
    $stderr = File.open(File::NULL, "w")
    $stdout = File.open(File::NULL, "w")
  end
  config.after(:all) do
    $stderr = original_stderr
    $stdout = original_stdout
  end
end