[ruby-core:36542] [Ruby 1.9 - Feature #4796] Coverage should be restartable

Issue #4796 has been updated by Xavier Shay.


> You are talking about second (or later) calls to Coverage.start, right?
Yes, that would be fine.

> I cannot understand why the feature is needed for this use case.
> Could you elaborate this?

It's not required, it just would of made my life easier. I was trying to integrate with the `parallel` and `SimpleCov` gems, and ended up with a work around which involves conditionally hooking at_exit and a file lock, which is a bit of a mess.

> Here is a patch.
I will try it out and report back. Thanks!
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Feature #4796: Coverage should be restartable
http://redmine.ruby-lang.org/issues/4796

Author: Xavier Shay
Status: Assigned
Priority: Normal
Assignee: Yusuke Endoh
Category: lib
Target version: 1.9.3


I would like a way to be able to make the following test past:

    require "test/unit"
    require "coverage"
    require 'tmpdir'

    class TestCoverage < Test::Unit::TestCase
      def test_restarting_coverage
        Dir.mktmpdir {|tmp|
          Dir.chdir(tmp) {
            File.open("test.rb", "w") do |f|
              f.puts <<-EOS
                def coverage_test_method
                  puts :ok
                end
              EOS
            end

            Coverage.start
            require tmp + '/test.rb'
            Coverage.result
            Coverage.start
            coverage_test_method
            assert_equal 1, Coverage.result.size
          }
        }
      end
    end

The problem is that `Coverage.start` doesn't track any files loaded before it is called. This is probably desired behaviour so that stdlib files are not tracked, but it limits the usefulness of Coverage. Specifically, I am trying to collate coverage reports from workers in multiple processes. Also I want to associate coverages with specific tests (this test executed this code, etc...). This is very difficult without being able to restart.

What would be involved in doing this? If you point me in the right direction I can perhaps have a go.



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