# Test coverage checking when test driver is separate from the

**URL:** <https://www.ruby-forum.com/t/test-coverage-checking-when-test-driver-is-separate-from-the/66057>\
**Category:** Ruby\
**Created:** [August 23, 2006, 2:52am UTC](https://www.ruby-forum.com/t/test-coverage-checking-when-test-driver-is-separate-from-the/66057 "2006-08-23T02:52:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![fmwr](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/9de053/32.png) [@fmwr](https://www.ruby-forum.com/u/fmwr)\
**Post date:** [August 23, 2006, 2:52am UTC](https://www.ruby-forum.com/t/test-coverage-checking-when-test-driver-is-separate-from-the/66057/1 "2006-08-23T02:52:18Z")

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Hello,

I have a program compiler.rb, that compiles something.  
The test driver is a separate program, that runs compiler.rb, then feeds  
the results to a virtual machine, and checks if it gets expected  
results.

Now I’d like to verify that every single line of compiler.rb is  
covered by tests.  
How can I make rcov merge information from multiple runs of compiler.rb  
?

---

<div class="post-metadata">

**Author:** ![fmwr](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/9de053/32.png) [@fmwr](https://www.ruby-forum.com/u/fmwr)\
**Post date:** [August 23, 2006, 1:11pm UTC](https://www.ruby-forum.com/t/test-coverage-checking-when-test-driver-is-separate-from-the/66057/2 "2006-08-23T13:11:11Z")

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On Wed, Aug 23, 2006 at 08:32:09AM +0900, Tomasz W. wrote:

> I have a program compiler.rb, that compiles something.  
> The test driver is a separate program, that runs compiler.rb, then feeds  
> the results to a virtual machine, and checks if it gets expected results.
> 
> Now I’d like to verify that every single line of compiler.rb is  
> covered by tests.  
> How can I make rcov merge information from multiple runs of compiler.rb ?

You can use the --aggregate option, which was added in 0.7.0.  
Essentially, you just have to run your program using rcov with the  
–aggregate FILE option:  
rm -f coverage.data  
rcov -t --no-html --aggregate coverage.data bin/compiler.rb – -args  
–to --compiler.rb bar.src  
rcov --aggregate coverage.data bin/compiler.rb – -some --other --args  
foo.src

You can skip HTML report generation in all but the last run with  
–no-html;  
the -t (text summary) option stops rcov from complaining about the lack  
of  
files to analyze.

There’s some additional information about how to do it both manually and  
with a  
Rake task at  
[eigenclass.org](http://eigenclass.org/hiki.rb?rcov+0.7.0)

Note that --aggregate is fairly slow since all the execution count and  
coverage information must be saved in the specified file, as well as the  
code  
that was loaded (since in a later execution different files could be  
loaded/parsed).

---

<div class="post-metadata">

**Author:** ![fmwr](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/9de053/32.png) [@fmwr](https://www.ruby-forum.com/u/fmwr)\
**Post date:** [August 23, 2006, 4:21pm UTC](https://www.ruby-forum.com/t/test-coverage-checking-when-test-driver-is-separate-from-the/66057/3 "2006-08-23T16:21:30Z")

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On Wed, Aug 23, 2006 at 08:08:27PM +0900, Mauricio F. wrote:

> On Wed, Aug 23, 2006 at 08:32:09AM +0900, Tomasz W. wrote:
> 
> > I have a program compiler.rb, that compiles something.  
> > The test driver is a separate program, that runs compiler.rb, then feeds  
> > the results to a virtual machine, and checks if it gets expected results.
> > 
> > Now I’d like to verify that every single line of compiler.rb is  
> > covered by tests.  
> > How can I make rcov merge information from multiple runs of compiler.rb ?
> 
> You can use the --aggregate option, which was added in 0.7.0.  
> […]

Sorry, I misread the first paragraph and answered somewhat aside of the  
question.

In the case you describe, you could create a small wrapper that would  
look  
more or less like this:

#!/usr/bin/env ruby

system(“rcov”, “–aggregate”, “coverage.data”, “–no-html”, “-t”,  
“compiler.rb”, “–”, \*ARGV)  
exit $?.exitstatus

Then you could select which script (the wrapper or the actual  
compiler.rb) is  
to be executed with a symlink.  
Alternatively, you could change the driver to select the script or  
execute  
rcov with the appropriate arguments directly, but at that point you’d  
have to  
implement some way to specify whether rcov is to be used or not, if you  
want  
to allow both.

Hope this helps.