It would seem that despite all fears to the contrary, Arena has actually sort of brought back the previously forgotten art of deckbuilding.
Sure, someone has always been building those decks, so it was never completely forgotten (except by WotC based on how badly they have missed on many, many interactions for years now), but at some points it seemed as if netdecking was much more of a thing than it had been previously. And yes, this is just shades. Most players will just netdeck and that is fine. Some people make movies, some people enjoy movies. Neither is bad in itself. Same should apply to netdecking (despite there been a lot of resistance early on).
The truth is that deckbuilding is a creative endeavor, so you need time to do it and experience to be good at it. However, it is important to remember that just writing down 60 cards on a piece of paper or putting together 60 cards on Arena is not in itself deckbuilding. It is only one part of the process. It isn’t like the screenplay is the same as the movie. It still needs a lot of steps to be the real thing. Okay, that’s not a very good analog, but think of a sketch versus a painting. That’s closer.
The Golden Rule
While I can provide you with various ideas on how to test, I can’t really give you a specific process, because that is highly individual. This is a learning process and people learn differently. The problem is that we are not very good at identifying how we learn, but this is at least in part because we are given options, that are not necessarily relevant. On the other hand, hopefully you are doing this because you are having fun, so you should test in a way that is enjoyable to you.
The Silver Rule
If you are working with other people, find a role for yourself. You should be enjoying yourself, but you should also make sure you are beneficial to the group of people you are working with. If they are using their time and resources to help you, you should also be helping them.
The Bronze Rule
Variance is good. Going out to the “real world” to test your secret deck is actually important and much more valuable than trying to actively hide your tech. I’ve seen this happen many times: Someone makes an assumption on what is going to be played in a specific tournament, then just sit back and play among friends, not paying attention to what’s going on in the meta, leading them into playing something that is perfectly constructed against decks that are not popular any more. So, while you should find a way to test that works for you, you should also try to cover your bases by doing more than noe thing. This actually also means that you shouldn’t trust what you see on Arena very much either. Many players will choose a deck they can get a lot of games in a short time and in a real tournament, they might play something very different. Also, certain players will play tier decks until they reach Mythic and after that they will play whatever, so your mileage may vary with how instructive playing on Arena can be.
Familiarize Yourself With the Cards
Obviously, this is going to be harder, if we are talking about a brew in Modern than Standard, but yes, you should be familiar with the cards. Scryfall helps if you know how to use it.
Example: You want to build a deck with Bard Class. So, you look at various legendary creatures, especially in green and red. However, if this is what you are up to, you might miss something like Hero's Blade.
You can’t do this on Arena (yet), but you can do this on XMage or on paper. WotC has stated in the past that proxying is fine and this is one purpose where it is actually very important. The professional teams generally used to test with proxies (before the pandemic), because they wouldn’t be able to get the full sets (or mostly full sets) as the major tournaments were very close to the release and they would often start testing before the set was even out. You will find weird cases you want cards for and that often means that you need to test weird cards you didn’t even think off beforehand.
Just be clear with your proxies. The other side of this is that if you don’t have the full rules text available and you just assume things, you might think cards work differently than they actually do.
This is an easy way to find some problems fast. It’s easier with aggro and combo decks, but you can try to figure out certain things with a control deck as well. On Arena, you have Sparky to do this, but obviously you can also this on paper and there are other services, such as TappedOut, which can be helpful as well. I like to use this especially to figure out my manabase. For example, once I realized that I should be playing Fiery Islet instead of Sunbaked Canyon in my Rakdos deck, because I was playing Shadow of Doubt and the Islet is better for casting that.
Find Test Opponents You Can Trust
Playing against random people on Arena, who concede immediately when there is any kind of a setback on Arena, is not very helpful in understanding your deck. Also, playing against people, who are not good enough, is not helpful either. If your opponent can’t good enough, they will make mistakes and thus the test doesn’t give you any actual information.
Don’t Concede Early… Or Do
One problem I keep seeing is that I’m losing my touch of the game, because most of the time when a game becomes complicated, my opponents on Arena will just concede rather than think it through. When you don’t have the opportunity to go through these situations, you are deprived of the opportunity to learn from them. So, try to see things through.
On the other hand, if you know that you can’t win, just concede. Don’t waste your time, if you can be doing something more productive. It’s just that finding a decent balance between these two can be difficult, but I would err on the side of seeing games through first, because you have an opportunity to see something you otherwise might miss.
Sit Back and Watch
I think this is very underappreciated in the age of Arena, but personally I’ve always found it helpful to follow games played by others. I have a more objective view of the situation and when I don’t have to care for the mechanics of the game, I can concentrate on the strategy. Sometimes it can also be helpful to discuss what’s going on even midgame, even if you are giving away information.
Talk to Others
Back when we used to actually test physically, we would often discuss various things about the decks. Individual card choices were a popular topic, especially the last card would often be discussed pretty much until the deck registration deadline.
If You Aren’t Sure About a Certain Decision, It Might Not Be that Important
Suppose you are playing Modern and you have six slots for one mana discard in your deck and you are not quite sure how many Thoughtseizes and how many Inquisition of Kozileks should you fit into that six? Most of the time you will have an idea based on the meta, but sometimes you just aren’t sure whether it should be three and three or four and two in favour of which ever. Well, here’s the way to approach that: If you have a very marginal decision, it doesn’t matter. You can use hundreds of games to figure out which is the right approach, but that usually means that you could be using this time for something more productive. If you can use your day to gain a .01% advantage or a 2% advantage, you should choose the latter.
Change Your Deck Often
When playing on paper, you should have a stack of options ready. Early on in the process, if you aren’t changing your deck at least every couple of games, you are doing something wrong. Sure, many of these changes will be reversed quite fast, but you still want to test a wide variety of options, especially in Standard, where sideboarding is often more about tinkering with the deck than putting in a bunch of hate cards. This can also help you find a transformative sideboarding strategy.
Play Sideboarded Games
Unless you are a very, very slow player and continuously encounter very, very slow players or matchups, you will play more sideboarded than first games. So, be familiar with your sideboard by playing it at least as much as your main deck. You will probably have to do a lot of theorycrafting here, as in many formats there are so many possible matchups, that you can’t test them all.
So, here’s a tip for testing sideboards for those older formats: Choose opening hands with key sideboard cards in them. Then if you notice that those cards aren’t helping, don’t put those cards into you sideboard. Also, since those sideboard spots are extremely valuable in these formats, don’t play them unless they can really change the outcome of the game. You need to optimize your sideboard as much as possible, so if a 20/80 matchup is changing into 30/70, you might just have to hope that you won’t meet these decks or find a new deck for yourself.
You also want cards that can help you in several different matchups, so that you can maximize the efficiency of those very valuable spots.
Don’t Overdo It
Your brain needs to be able to relax and recover. Sure, some people can play without tiring for ages, but there’s a reason why Kai Budde was able to win 7 Pro Tours. He just never needed to stop, but there’s also a reason why this record will probably never be broken. It’s no use to burn yourself out before a tournament, so remember to have breaks and do something besides just play. Go for a walk or something.
It can be helpful to do this. You have some actual basis when trying to explain why you should play a certain deck or a certain version of a deck.
Trust Your Instincts
You can never get enough games to be statistically credible. Therefore, you should rely on your instincts. Your instincts are basically a shortcut to something you know, but you don’t know you know it. Just be careful with this. You can overdo it.
Just remember that this needs to be fun, so approach it that way.