In many jurisdictions this test has been superseded by the concepts of similarity and likelihood of confusion, due to the harmonizing effects of the Agreement on Trade-Related Aspects of Intellectual Property Rights.
Mark X may share elements of spelling or style that would lead a reasonable observer to believe the trademarks were related.
The reputation attaching to a trademark is also significant, such that "Microsafe" or "Micro Software", although clearly not identical, could potentially be confusingly similar and amount to an infringement.
Cases of this type can be proven by using surveys which show that members of the public who are likely to use the services or goods protected by the trade mark have been confused by it.
[1] In the 2019 Canadian Federal Election the satirical Rhinoceros Party ran a candidate by the name of Maxime Bernier in the riding of Beauce.