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Testing terminal output with RSpec

Arne Hartherz
July 05, 2016Software engineer at makandra GmbH

When testing Ruby code that prints something to the terminal, you can test that output.
Since RSpec 3.0 there is a very convenient way to do that.

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Anything that writes to stdout (like puts or print) can be captured like this:

expect { something }.to output("hello\n").to_stdout

Testing stderr works in a similar fashion:

expect { something }.to output("something went wrogn\n").to_stderr

Hint: Use heredoc to test multi-line output.

expect { something }.to output(<<-MESSAGE.strip_heredoc).to_stdout
  Dear Bob,
  greetings!
  
  Love,
  Alice
MESSAGE
Posted by Arne Hartherz to makandra dev (2016-07-05 11:11)