Test (3)

"So, you suspect your wife heals others harmed by holy weapons and she might be immune to it which makes her a very hard-to-kill pureblood. The problem you have is how you have to test it, which is to cut her. You can't do that," Lucas said, checking that he had everything right. 

If what Xavier said was true then Selene had a whole lot more problems coming her way. A vampire who couldn't die from holy weapons and might be able to heal others would be valuable.

The very people who turned their backs on Selene now or judged her would want to get close to her so they had a way of healing.

It was worth testing if such a pureblood existed but Lucas understood why Xavier didn't want to take the chance to cut Selene. If he was wrong, then Selene would have a cut on her hand which would never heal forever.