Our typical setup is this: we have a mailing with dynamic content (sometimes rather extensively) and from the mailing we link to a WCA landing page, which also has similar personlization rulesets.

Now to properly test the different rules in a mailing we can use a testlist where every contact has a set of value so we can see if all the possible combinations of the personalization rules work.

A landing page however, when linked to from a test mailing, does not use contacts (and their field values) from the test list. It falls back to the parent database, which might

a) not have the record, which is present in the test list at all OR
b) have the contact but we different field values thus not usable for testing the aforementioned personalization rulesets on the landing page