Should we be using specs with create_templatesymlink and hash_including?

Coming from !4808 (diffs, comment 460786817)

We have a pattern in our specs of

expect(chef_run).to create_templatesymlink('foo').with_variables(
  'bar' => 'blah',
  'baz' => 'more blah'
)

Checking with_variables does not guarantee that the template foo actually uses any of the passed variables. In my mind, we should be checking here for actual content generated.

So I'd propose we make a point to prefer testing for generated content. It is still valid to verify that the specific variables are getting passed. But I feel that usually, we care more about the end content.

/cc @gitlab-org/distribution