Adding regression testing of top-100 websites with invariant analysis

Layout tests could not be extended with real online websites such as top-100 (top-300) lists due to the changing content. However, it would be possible to extract a set of invariant attributes for these sites, such as basic layout, number of links, etc, and use these attributes as a base for comparison to expected attributes.

The invariants need to be determined first by hand and then encoded in a unified description as a testing oracle which is suitable for automatic processing. The actual invariant attributes could be determined based on rendering information and this way the comparison could be performed completely automatically.

The manual analyis of top-100 websites have been performed and now we are working on formalizing the attribute set.