I'm going to break with tradition and side will Bill on this one. At least kinda-sorta-side with him.
The thing with a lot of matters of personal testimony is that they are, well, personal. I know what God has done in my life but there's no way I could offer anyone reading this a shred of evidence that I'm not making it all up. For all you readers know I could be a child-eating, goat-sacrificing devil worshipper just flicking through the Bible and putting forward some arguments to see how long I can keep up the charade. Just to avoid any doubt, I'm none of those things, but you only have my word for that
Where healings are concerned some of us will have seen miraculous healings, and yet have no concrete evidence to show to another to prove the fact. But we know what we've seen. As one man Jesus healed said, "I was blind but now I see". He didn't need to know anything else, he knew that this man Jesus gave him his sight. What evidence do we have that it ever happened, aside from a passage in an old book? The issue here is whether we consider that old book to be credible or not. Likewise if someone reports a healing we have to decide whether that person is credible or not, in the absence of evidence.
This is where I have major issues with these so-called "international ministries". They make grand claims of things that happened to Someone Else, Somewhere Else, usually with little to no evidence, and expect it to be believed. It's so totally unlike the lame beggar at the Beautiful Gate where everybody knew him, everybody knew he was lame and everybody could see him jumping and leaping and praising God. Miracles that bring glory to God locally are good, claims of miracles that seem to do little more than attempt to validate a ministry or give extra authority to the latest grand speaker are probably worth regarding with some suspicion.
Where those ministries are concerned, Jesus said we would know them by their fruit. I have never met the likes of Bill Johnson, Kenneth Copeland, Creflo Dollar etc and probably never will. I won't get to see the fruit of the lives. But I can see the teachings they make public and follow the Scriptural call to "test all things, hold fast what is good". If their teachings don't align with Scripture (or worse, contradict Scripture) then that invalidates any signs and wonders that might be associated with them. As God told Moses in Deut 13 a prophet who makes correct predictions should still be ignored if he then urges the people to follow other gods. A teacher who performs signs and wonders but does not point to the one true God should be disregarded.