Mock is a tool which builds a package using rpmbuild in a 'cleanroom' environment. This has several advantages:* it tests the completeness of the BuildRequires in the spec file* it avoids the installation of a lot of tools (BuildRequires) on the main host system* it permits different tools and tool versions to be used for the build than are installed on the host (e.g., building for F18 on an F16 system) Background information on using Mock:* [[:fedora:Using_Mock_to_test_package_builds|Using Mock to test package builds]]