VE-1588: Tests for ve.dm.WikiaTemplateModel

Because we make an API request to get all available parameters for a given template, we need to ensure that we don't add all of the empty parameters in the serialize() and getWikiText() methods. This test tests for this scenario.
Should be provided as a second parameter to test method. Expect is to be used when you are dynamically creating test cases and don't know how many there will be.