Test coverage is one of the concrete measurements that you can use in XP projects.

There are some tools on the market that measure CodeCoverage. Applying those to your TestSuite make up the TestCoverage.

One of those tools is Clover (http://www.thecortex.org/clover).

It grants free licenses to OpenSource project.

You can explore the use of this tool live and online e.g. with the CanooWebTest project.

-- DierkKoenig

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See also CompleteCoverageIsExpensive
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CategoryTesting