General Strategy
Neutral
Defense
Your primary defensive options include Grave Digger and c.SGuardAllStartup1Recovery16Advantage-7. Both of them are typically weak defensive options despite one of them being a 1f normal. Missing Link things.
Grave Digger (236SGuardMidStartup9Recovery25Advantage+1) is your viable guard cancel option. You can use the other ones if you want to be funny, but 236S is the one that will work occasionally. It doesn't have any invulnerability and typically takes 12f~ or more to hit grounded opponents, making using it against Charge Cancel (or general multi-hit gatling into special) pressure usually very fallible. It is, however, entirely air unblockable with a large hitbox to boot, allowing it to dismantle certain air approaches very effectively, so there's that.
c.S is a 1f normal that leads into your best combos on hit and your pick of pressure on block. Misfortune strikes, however: its proximity activation range is incredibly small, especially in comparison to most other gameplan-important c.S normals, like Ky or Kliff's. Its actual hitboxes are also small, with the 2nd hit whiffing on most characters crouching and some standing; while the 3rd is incapable of hitting non-tall characters at all while grounded, making hitconfirming it sometimes much rougher than you'd like. Failing to press c.S in proximity range will result in you pressing f.SGuardAllStartup13Recovery36Advantage-17, a significantly slower normal which will result in you getting hit into either an OTG infinite or a regular ol' Charge Cancel infinite. Which is bad.
6PGuardAllStartup4Recovery13Advantage-7 can be used as an alternative abare option, being slightly slower than c.S at 4f. On the other hand, it boasts usable multi-hits for hit confirms as well as solid range, while confirming into much of the same things that c.S would. 2PGuardLowStartup6Recovery8Advantage-1 and 2KGuardLowStartup6Recovery18Advantage-8 are viable alternatives as well with their own sidegrade attributes.
Though it couldn't necessarily be described as "defense" in terms of "what you should do when you start blocking", Testament's best option to deal with close-range pressure is to deter it from happening with traps. Their 236P (Phantom Soul)GuardAllStartup18RecoveryAdvantage+3 is capable of deterring most forward dash and airdash approaches (at least, usually not letting them run offense on you if they're dashblocking to get through it), and lasts long enough to to set up more traps thereafter.
623S (Panzer Centipede)GuardUnblockableStartup95RecoveryN/AAdvantageN/A is also a surprisingly useful defensive measure to set up, both when Phantom Soul works and when it doesn't. It persists regardless of what happens to Testament, including if they're currently stuck in an infinite, which ironically makes its extremely long delay before resurfacing a bit of a boon at times. Panzer combo breaking the opponent or otherwise scaring them from pushing additional offense is its most useful feature by far, and it is difficult to properly OS due to being unblockable. Due to its slow speed, it can be difficult to get an opportunity to apply against aggressive opponents who are not willing to give you a bit of grace for playing Bottom 1 (which will be most of them in actual competitive play, but this is Missing Link).
Offense
Fighting Testament
Every character's OTG infinite on Testament is as follows:
Assume any rep to have a short amount of walking or dashing to close distance as typically the launching normal will have a decent amount of knockback but the time for a followup is incredibly lenient beyond what you would expect so feel free to get point blank usually.
- Potemkin:
2K > 623RxN
- May:
2H > 236RxN
- Ky:
corner only, walk to adjust: launch (623H, 63214K) > 623SxN
(not consistent, a CC infinite is recommended) - Kliff:
2K > 236RxN
- Baiken:
2K > 236RxN
- Chipp:
2H > 623RxN
OR623PxN
- Zato:
2K > 22RxN
- Baldhead:
(j.K) > j.236SxN
(don't do this) - Axl:
2SxN
- Sol:
2K > 623RxN
OR66KxN
- Millia:
623SxN
- Testament:
2KxN
- Justice:
41236SxN
OR421KxN
(second one is significantly harder but also significantly cooler)
For most CC infinite characters, this is a more difficult BM optimization that takes years to kill, but in the event that you get a launch hit from otherwise practical parts of your kit (IE: Sol's Dashkick) it's always nice to know that you can kill off it.