[Q] changing a stream of 'print' method to a string

ruby-talk
1

Hi,

I have a question.
How to change a stream of ‘print’ to a string? Is it able?

Background:
I want to test my program which print data to standard output.
And I have no good idea to test output data.

··· 
##
## main.rb
##
def print_list(list)
  list.each_with_index do |item, index|
    print "#{index+1}: #{item}\n"
  end
end
----------------------------------------

----------------------------------------
##
## test program
##
require 'main'
require 'runit/testcase'
require 'runit/cui/testrunner'

class MainTest < RUNIT::TestCase
  def test_print_list
    list = [10, 20, 30]
    print_list(list)        # <== how to test?
  end
end

testcases = MainTest.test_cases()
RUNIT::CUI::TestRunner.run(testcases)
----------------------------------------

If I could change a stream of print to a string, I would write it
like the following:

----------------------------------------
  ...(snip)...

  def test_print_list
    list = [10, 20, 30]
    expected = <<END
1: 10
2: 20
3: 30
END
    result = ''
    result << print_list(list)     # if I could
    assert_equal(expected, result)
  end

  ...(snip)...
----------------------------------------

Please give me an advice.

–
regards,
makotz kuwata

2

I’m not sure I understand your question, but the code you are trying to
write seems to work fine:

$ irb

result = “”
=> “”
result << “Hello”
=> “Hello”

Is this what you want?

···

On Wed, Mar 26, 2003 at 09:45:21AM +0900, makotz wrote:

Hi,

I have a question.
How to change a stream of ‘print’ to a string? Is it able?

Background:
I want to test my program which print data to standard output.
And I have no good idea to test output data.

----------------------------------------
##
## main.rb
##
def print_list(list)
  list.each_with_index do |item, index|
    print "#{index+1}: #{item}\n"
  end
end
----------------------------------------

----------------------------------------
##
## test program
##
require 'main'
require 'runit/testcase'
require 'runit/cui/testrunner'

class MainTest < RUNIT::TestCase
  def test_print_list
    list = [10, 20, 30]
    print_list(list)        # <== how to test?
  end
end

testcases = MainTest.test_cases()
RUNIT::CUI::TestRunner.run(testcases)
----------------------------------------

If I could change a stream of print to a string, I would write it
like the following:

----------------------------------------
  ...(snip)...

  def test_print_list
    list = [10, 20, 30]
    expected = <<END
1: 10
2: 20
3: 30
END
    result = ''
    result << print_list(list)     # if I could
    assert_equal(expected, result)
  end

  ...(snip)...
----------------------------------------

Please give me an advice.

–
regards,
makotz kuwata

–
Daniel Carrera
Graduate Teaching Assistant. Math Dept.
University of Maryland. (301) 405-5137

en banc: en banc (ahn-BAHNK) adjective, adverb
Having all the judges of a court present in a hearing.

3

def print_list(list, out=STDOUT)
list.each_with_index do |item, index|
out.print “#{index+1}: #{item}\n”
end
end

In your test case:

require ‘stringio’

buf = “”
StringIO.open(buf, ‘w’) do |io|
print_list(list, io)
end

assert_equal(expected_result, buf)

I think I got that right.

Gavin

···

On Wednesday, March 26, 2003, 11:45:21 AM, makotz wrote:

I have a question.
How to change a stream of ‘print’ to a string? Is it able?

Background:
I want to test my program which print data to standard output.
And I have no good idea to test output data.

----------------------------------------
##
## main.rb
##
def print_list(list)
  list.each_with_index do |item, index|
    print "#{index+1}: #{item}\n"
  end
end
----------------------------------------
4

Or you can just do
$defout = StringIO.open(…)

I think that should let everything work without changes, except putc under
1.6.8 (but then you don’t get stringio with 1.6.8 unless you install the
1.6->1.8 shim)

Regards,

Brian.

···

On Wed, Mar 26, 2003 at 09:58:11AM +0900, Gavin Sinclair wrote:

def print_list(list, out=STDOUT)
list.each_with_index do |item, index|
out.print “#{index+1}: #{item}\n”
end
end

In your test case:

require ‘stringio’

buf = “”
StringIO.open(buf, ‘w’) do |io|
print_list(list, io)
end

assert_equal(expected_result, buf)

5

Thank you, Gavin.
‘stringio’ is very useful. I didn’t know it.
It seemed to be a feature of Ruby 1.8, so I installed Ruby Shim.
http://raa.ruby-lang.org/list.rhtml?name=shim-ruby16_18

regards,
makotz

···

Gavin Sinclair gsinclair@soyabean.com.au wrote:

def print_list(list, out=STDOUT)
list.each_with_index do |item, index|
out.print “#{index+1}: #{item}\n”
end
end

In your test case:

require ‘stringio’

buf = “”
StringIO.open(buf, ‘w’) do |io|
print_list(list, io)
end

assert_equal(expected_result, buf)

I think I got that right.

Gavin