From: Will Parsons <oudeis@...>
Date: 2009-02-05T10:39:31+09:00
Subject: Re: custom assertion message for unit tests

Rob Biedenharn wrote:
> 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?
>
> 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

This is certainly an improvement on my version, but it is not completely
satisfying - the reason being that by explicitly converting the permissions
to a string they get displayed as strings, i.e., I would like to see:

  <755> expected

rather than:

  <"0755"> expected

> 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

I'm not sure I understand this - what's the advantage of defining the
assert_mode method over using the already defined methods?

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

Yes, because I want also to check for being read-only in addition to being
executable in the file permissions.

-- 
Will