This depends on the point of view. Technically they (the tests) are performed pretty accurate. This does mean all the products are tested in the same conditions with the same criterias on the clean XP Prof install on the same computer. You can check every result yourself as long as all the tests are published. Though, there is a big concern about the results logical consistency. So you can disregard the result but take product report and make your own conclusion.
The have been discussed to death here. Do we really need a new thread. To the OP do a search on matousec and read to your hearts content.
Leaktests suck. Install a good AV or be carefull when browsing the web and you'll be safe from the so-called "leaks". Man, "leaktests" are just plain stupid.