1. You went on vacation together and everything went wrong.
It's very likely this was your first vacation together, so you probably wanted everything to be perfect but then oh, nope. Your hotel TV only had basic cable and the internet was spotty and you couldn't figure out which gate you were supposed to be at because the airport kept changing it. If you were able to weather that without thinking about what your ex is up to right now because his Instagram makes it seem like he's single now, you're golden.
2. You went on a road trip to literally anywhere together.
Listen, if you're driving with your partner to anywhere farther than the grocery store you always go to or the really good Forever 21 that's 20 minutes away, you're going to either get antsy or bored or exhausted or punchy. They're going to want to listen to Nickelback and you're going to want to listen to Beyoncé and nothing but Beyoncé. The opportunity to go from "Yay! Six-hour road trip to the beach that's better than our normal beach!" to "You didn't bring enough snacks and you drank the last water? Fuck you, Drew," is very real. But pulling up to your home at the end and still liking each other = love.
3. You met their parents and they didn't totally like you at first.
Meeting the parents will always be stressful. Meeting them and having them love you? Easy. But if you met their parents and they weren't too sure about you and you were able to figure out how to get through that together without a massive argument about how their parents are snobs and they're lucky to have you, keep this one.
4. You had major issues with one of their good friends.
I've definitely had friends whose girlfriends were dicks when I first met them, and there was a part of me that was like, "Dude, drop this girl. Now," but I'm actually glad when some of them didn't. Sometimes people just get nervous, and you and your partner and your friends have to work out the kinks (e.g.: he doesn't like your friend Brian because he thinks you're into him and then you calmly introduce him to Brian's girlfriend Gina). And other times you're Max's girlfriend Sheila who sucks, but that's my issue and I'll deal with it later.
5. You were on an airplane and started fighting.
Why? Who knows why? Because there weren't little TVs on the plane, because there were little TVs but you only had one set of headphones, because you got the last bag of peanuts and didn't want to share. There are plenty of reasons to fight on a plane (and even worse, you have nowhere to retreat to because you're sitting next to each other no matter what), so if you can hit the tarmac still wanting to bone and hold hands, you're aces.
6. Going to a party where they know everyone and you don't.
I know this is just awkward, but if you're willing to go through the social nightmare that is eating chips out of boredom, sitting on an empty couch by yourself, and laughing at inside jokes you couldn't possibly understand because you love the person that much, I do not worry for your future.
7. Being at a wedding together and having it not be weird.
It's totally normal to be at a point in a relationship where being at a wedding together is mostly full of you staring at each other awkwardly, like someone farted and you're not sure who. However, if you can openly watch two people committing their lives to one another and both feel like it's something wonderful you get to share together instead of something you want to dodge, that's a good sign.
8. Figuring out how to decorate your shared apartment.
I don't know if two people have ever had exactly the same decorating style in the history of couples ever, so agreeing that, "OK, so now our dining room table is going to be ugly in my eyes for all of eternity but you think it's gorgeous" is a sign you're healthy people.
9. When both of you haven't eaten all day and neither of you knows what you want to eat.
This could so easily turn into a murder/suicide situation that if one of you is able to grab the phone and order pizza (and you both realize you both really wanted pizza this whole time), you should just get married right then and use the pizza menu as a ring (somehow).