One of the things that I think applies to more than just this comes from a Christian psychologist who's book is currently on my reading list, is named Mark Yarhouse. One of the things he talks about is how too often we forget that when we first meet people, we're not meeting them in chapter 1 of their life. I ultimately don't really think there is just one test, at least yet, that we can always say "yes, you have genuine gender dysphoria", but we do need to be mindful that these people have often had a very difficult life up to whatever point that we are meeting them at and we need to be sensitive to them.
I liked what he said about how "You don't get to pick your causes" because that's the same thing that happened to me. I really knew nothing about the issue or anything about it.Then, I come back from Spring Break my senior year of college to my best friend in this weird state of frantic, yet distraught depressive and anxious state. They had gone home for his last Spring Break, and I asked what happened. They told me that they came out to their family as transgender after years of struggling with it, and his family wanted nothing to do with them anymore. I didn't know what to say or do, I said that I would help them through this struggle. They broke down crying, I had never seen them cry before, saying that they had tried so hard to be not even a Godly man, but just a man and just couldn't, and was done wearing a mask. I asked them if their therapist knew (I knew he had had depression for years), and they said yes, in fact, one of their diagnoses was "Gender Dysphoria". Looking back on it, there were definitely very subtle signs that it was there when we were growing up together, and it did always seem like something was bothering them or at least on their mind. They said something to me that stuck with me that night "I would rather lose everyone and everything than live with this. I want to experience those things called peace and joy that everyone else keeps talking about." Yes, they are a Christian.
Anyway, the started hormones early the next fall and it was like night and day immediately. Everyone who knew them could immediately tell there was a difference. My best friend talked a lot about noticing that there was this mental clarity and peace they'd never felt before. There was one day they said "This is what this joy thing everyone keeps talking about it." She's now in a much better place than she ever had been as male, nobody who has kept in touch wishes or wants the male version back. We all love her because it's so much better for her. She feels closer to Christ, her relationship with God has never been better. She is celibate and doesn't date because she believes that same-sex relationships are wrong, though we all joke with her she should find a nice transman, but she's not into men. Over those months, I realized that I, and quite frankly, the entire conservative position on it has it wrong. I've met a few other Christian transgender people through her and they all have similar stories of struggling with their identity in Christ and their dysphoria, and other transgender people through her. All of them have said the only thing that made their dysphoria better is transitioning.