Testing your code is important! Before you can even get your code committed into the source tree, you have to test it, and larger patches have to have automated tests. These articles will help you master (and continue to excel at) testing Mozilla code.
Clang has a built-in static analyzer. The gist is you add a wrapper around the compiler which directs all static analysis results to a common location. At the end of a build, these reports are aggregated into a report document showing all the potential issues.