From: Rob Biedenharn <Rob@...>
Date: 2009-02-05T09:34:40+09:00
Subject: Re: custom assertion message for unit tests

On Feb 4, 2009, at 5:59 PM, Will Parsons wrote:

> I'm having trouble trying to figure out how to customize an assertion
> message when running unit tests.  In particular, I want to check the
> permissions on a file, so I have something like:
>
> assert_equal(0755, File.stat(test_file).mode & 0777)
>
> If it fails, I get a message like:
>
> <493> expected but was
> <420>.
>
> and of course I would like the expected and actual permissions to be
> displayed in octal rather than decimal.  How can I do that?
>
> --  
> Will


Perhaps something like:

$ ruby -r'test/unit'
class SomeTest < Test::Unit::TestCase
   def setup
     @test_file = 'some_file'
     File.open(@test_file, 'w') {|f| f.write "Hello!"}
   end
   def test_bad_file_mode
     File.chmod(0644, @test_file)

     assert_equal '0755', '%#o'%[File.stat(@test_file).mode & 0777],  
"Mode of #{@test_file}"
   end

   def test_good_file_mode
     File.chmod(0755, @test_file)

     assert_equal '0755', '%#o'%[File.stat(@test_file).mode & 0777],  
"Mode of #{@test_file}"
   end
end
__END__
Loaded suite -
Started
F.
Finished in 0.025823 seconds.

   1) Failure:
test_bad_file_mode(SomeTest) [-:9]:
Mode of some_file.
<"0755"> expected but was
<"0644">.

2 tests, 2 assertions, 1 failures, 0 errors


Note that I'm doing the conversion to octal myself with the '%#o' and  
String#%

It would be better to pull this into a helper method:

$ ruby -r'test/unit'
class SomeTest < Test::Unit::TestCase
   def assert_mode(expected_mode, actual_mode, message=nil)
     assert_equal '%#o'%expected_mode, '%#o'%actual_mode, message
   end

   def setup
     @test_file = 'some_file'
     File.open(@test_file, 'w') {|f| f.write "Hello!"}
   end
   def test_bad_file_mode
     File.chmod(0644, @test_file)

     assert_mode 0755, File.stat(@test_file).mode & 0777, "Mode of  
#{@test_file}"
   end

   def test_good_file_mode
     File.chmod(0755, @test_file)

     assert_mode 0755, File.stat(@test_file).mode & 0777, "Mode of  
#{@test_file}"
   end
end
__END__
Loaded suite -
Started
F.
Finished in 0.0107 seconds.

   1) Failure:
test_bad_file_mode(SomeTest)
     [-:3:in `assert_mode'
      -:13:in `test_bad_file_mode']:
Mode of some_file.
<"0755"> expected but was
<"0644">.

2 tests, 2 assertions, 1 failures, 0 errors


Do you really want
   assert File.stat(@test_file).executable?
instead of a specific mode?

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com