Comments on: RCOV C0 line coverage more generous than EMMA’s C1 line coverage

By: Jamie Flournoy

Jamie Flournoy — Sun, 05 Aug 2007 04:20:42 +0000

>I’m wondering why you didn’t point that out?
I linked right to the very thing you’re saying I failed to point out.

Here’s what you’re apparently not grasping: the EMMA web site doesn’t talk about rcov, and the rcov web site doesn’t talk about EMMA. Likewise with Clover. The web sites for EMMA and Clover don’t talk about their functionality in terms of C0 vs. C1 vs. C2, but rcov does.

This post *compares* EMMA and rcov, and uses the *same terminology* (C0/C1) on both, with an identical code example for 2 different programming languages. I also talk about reasonable expectations for coverage % based on personal experience.

By: Jim Deville

Jim Deville — Sun, 05 Aug 2007 01:21:40 +0000

I just wanted to point out that even the creator of rcov points this out. The page you link to goes on to explain C0, C1, and C2 coverage. I’m wondering why you didn’t point that out?

By: John

John — Wed, 01 Aug 2007 04:30:15 +0000

My last comments formatting didn’t work so well. Maybe this will be better.

===

Hi Jamie,

Perhaps you know about this already, but if not…

You wrote:

====
There’s a little voice in my head that says, “Come on, you slacker, you should make it possible to dynamically break the database configuration and remount the root filesystem as read-only during the test suite so that the error handlers can all be 100% covered!”
====

One thing that I’ve done to increase test coverage is to reopen classes, and redefine methods that allow me to fail certain operations (for instance saving). Here’s an example:

class PictureStream
cattr_accessor :fail_saves
@@fail_saves = false

alias_method :unaliased_save, :save
def save(param = nil)
return unaliased_save unless @@fail_saves
false
end
end

This code goes inside one of my tests (test/units/whatever_test.rb), and when I have a test for failing to save, the code does this:

PictureStream.fail_saves = true
… do the operation …
… check that it failed …

When I run rcov on these tests, it tells me that the test did indeed cover the case where a save failed, allowing me at least some sense that things are working right.

Perhaps you’d seen this before, and I know it won’t help to produce a read only root filesystem, but I found it really useful to push up the amount of code that was covered by my tests.