Method: Minitest::Assertions#capture_subprocess_io

Defined in:

lib/minitest/assertions.rb

#capture_subprocess_io ⇒ Object

Captures $stdout and $stderr into strings, using Tempfile to ensure that subprocess IO is captured as well.

out, err = capture_subprocess_io do
system "echo Some info"
system "echo You did a bad thing 1>&2"
end

assert_match %r%info%, out
assert_match %r%bad%, err

NOTE: This method is approximately 10x slower than #capture_io so only use it when you need to test the output of a subprocess.

# File 'lib/minitest/assertions.rb', line 537

def capture_subprocess_io
  _synchronize do
    begin
      require "tempfile"

      captured_stdout, captured_stderr = Tempfile.new("out"), Tempfile.new("err")

      orig_stdout, orig_stderr = $stdout.dup, $stderr.dup
      $stdout.reopen captured_stdout
      $stderr.reopen captured_stderr

      yield

      $stdout.rewind
      $stderr.rewind

      return captured_stdout.read, captured_stderr.read
    ensure
      $stdout.reopen orig_stdout
      $stderr.reopen orig_stderr

      orig_stdout.close
      orig_stderr.close
      captured_stdout.close!
      captured_stderr.close!
    end
  end
end