Issue #9508 has been updated by Sam Rawlins.


Hi Eric, thanks for that test. It revealed my poor choice for `#define RUBY_EVENT_MCOVERAGE 0x040000` (`RUBY_INTERNAL_EVENT_SWITCH` is the same). I've updated my pull request with better choices in `include/ruby/ruby.h`: https://github.com/ruby/ruby/pull/511.patch

Another design question: I think that block calls should probably also be considered part of "Method Coverage" (which would then be renamed to "Function Coverage", tracking both method and block coverage). One big design problem here is that it is common to chain several blocks in one line, like iterators. Should I put in the work to track block coverage now, or wait until after this gets merged?

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Feature #9508: Add method coverage and branch coverage metrics
https://bugs.ruby-lang.org/issues/9508#change-45652

* Author: Sam Rawlins
* Status: Open
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
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Since the Coverage extension was introduced in Ruby 1.9, Ruby has had built-in line code coverage. Ruby should support more of the basic code coverage metrics [1]. I have a pull request on GitHub ( https://github.com/ruby/ruby/pull/511 ) to add Method Coverage (Function Coverage) and Branch Coverage. I'd love feedback to improve it.

Currently, with this feature, Coverage.result would look like:

    {"/Users/sam/code/ruby/cov_method.rb" => {
      lines: [1, 2, 2, 20, nil, nil, 2, 2, 2, nil, 0, nil, nil, nil, 1, 0, nil, nil, 1, 1, nil, nil, 1],
      methods: {1=>2, 15=>0, 19=>1},
      branches: {8=>2, 11=>0}
    }}

which includes
* the current Ruby line coverage report,
* as well as a method report (The method defined on line 1 was called 2 times; the method on line 15 was called 0 times; ...),
* and a branch report (the branch on line 8 was called 2 times; the branch on line 11 was called 0 times).

Branches
--------

Branches include the bodies of if, elsif, else, unless, and when statements, which are all tracked with this new feature. However, this feature is not aware of void bodies, for example:

    if foo
      :ok
    end

will report that only one branch exists in the file. It would be better to declare that there is a branch body on line 2, and a void branch body on line 3, or perhaps line 1. This would require the keys of the [:branch] Hash to be something other than line numbers. Perhaps label_no? Perhaps nd_type(node) paired with line or label_no?

More Coverage
-------------

I think that Statement Coverage, and Condition Coverage could be added to this feature, using the same techniques.

Caveats
-------

I was not very clear on the bit-arrays used in ruby.h, and just used values for the new macros that seemed to work.

Also, I would much rather use Ranges to identify a branch, so that a Coverage analyzer like SimpleCov won't need any kind of Ruby parser to identify and highlight a full chunk of code as a tested branch, or a not tested branch. I'm trying to find how that could be implemented...

[1] Wikipedia has good definitions: http://en.wikipedia.org/wiki/Code_coverage

---Files--------------------------------
pull-request-511.patch (26.7 KB)
pull-request-511.patch (38.5 KB)
pull-request-511.patch (57 KB)


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