From: Mauricio Fernandez <mfp@...>
Date: 2006-03-20T21:12:26+09:00
Subject: Re: capturing the stdout

On Mon, Mar 20, 2006 at 07:39:02PM +0900, Robert Klemme wrote:
> >I am running a test case and need it capture the output it gives me.
> >
> >require 'stringio'
> >old_stdout = $stdout
> >$stdout = StringIO.new
> >...........
> >@reqout = $stdout.string
> >$stdout = old_stdout
> >
> >
> >the above code captures the stdout if something written explicily (like 
> >puts).
> >but it doesnot capture the output or running a testcase.
> >i want to capture the results if the testcases.
> >is there a way it could be done.
> 
> You probably must redirect $defout also.  Other than that doing it 
> externally (i.e. in the calling process) might be an option, too.

IIRC $defout is deprecated.

You can separate the output (from the code being tested) from the information
displayed by Test::Unit as follows:

include Test::Unit::UI
out = StringIO.new ""
test_out = StringIO.new ""

$stdout = out
ret = Console::TestRunner.new(my_test_suite, NORMAL, test_out).start
$stdout = STDOUT
# "actual" stdout in out.string
# Test::Unit info in test_out.string


If you also want to capture the stdout from subprocesses, you need something
like
  begin
    old_stdout = STDOUT.dup
    STDOUT.reopen("mytempfile", "w")
    ...
    # create the TestRunner, possibly redirecting its output as shown above;
    # fork, system, ``, etc. in the tested code will be redirected to the
    # tempfile
    ...
  ensure
    STDOUT.reopen(old_stdout)
  end


Silly example of the former:


RUBY_VERSION                                       # => "1.8.4"
require 'stringio'
require 'test/unit/ui/console/testrunner'

class Foo
  def foo(a,b)
    if b > 3 
      puts a + b
    else
      puts a - b
    end
   
    a * b
  end
end
 
class TC_Foo < Test::Unit::TestCase
  def setup; @foo = Foo.new end
  
  def test_foo
    assert_equal(8, @foo.foo(2, 4))
  end
end

include Test::Unit::UI
out = StringIO.new ""
test_out = StringIO.new ""

$stdout = out
ret = Console::TestRunner.new(TC_Foo.suite, NORMAL, test_out).start
$stdout = STDOUT

puts "Output:"
out.string.each{|x| puts "-> #{x}"}
puts "----"
puts "Test (#{ret.passed? ? "passed" : "failed"}):"
test_out.string.each{|x| puts "->> #{x}"}
# >> Output:
# >> -> 6
# >> ----
# >> Test (passed):
# >> ->> Loaded suite TC_Foo
# >> ->> Started
# >> ->> .
# >> ->> Finished in 0.000601 seconds.
# >> ->> 
# >> ->> 1 tests, 1 assertions, 0 failures, 0 errors

-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby