This is the way I read this:
- There are TWO URLs, both having the same (key)words in URL, but one uses hyphen as a separator and the other does not, for example:
www.example.com/bluewidgets
www.example.com/blue-widgets
- Both URLs will have a new unique content (including unique page title and meta description).
- Both URLs will target the same keyword(s)
In this case, here is what I think:
It depends on the content. If the content of these two pages is sufficiently different and both contents are useful to visitors, I do not see any Google problems (in terms of getting some sort of penalty).
If the content of page y is just re-hashed page x, then this is issue that Panda algo is focusing on. However, if this is only one pair of such pages on a fair quality site, I do not think you would need to worry about Panda issue.
But I would echo netmeg's question:
(I'm completely unclear as to what the end result is supposed to be here)
What are you trying to test?
If you are testing effect on Google ranking, what you may want to consider is that these two pages would compete in Google with each other and that Google may filter one of them out or rank both of them lower than it would rank one stronger page.
So for this reasons if you are testing Google ranking, the test is flawed.