When testing a hero, you can test every hero (excluding Common Tier Heroes) at level 240 and its ascension level (Ascended, Legendary+, or Common).
As of Patch v1.45, it is possible for a hero to be tested using the Arena of Trials feature where you can test the hero twice. One using the original Test Hero feature and the other in a PvE comp with other heroes you've unlocked. Starting with Drez, players can also earn rewards in this feature for a limited time.
Testing a Hero
If you want to test a hero, you have to select the Heroes section in the User Interface below. Next, select the Portraits tab next to the Heroes Tab. Then, select the hero you wish to test and click the Arena of Trials section on the lower right corner of the game and click on the Wooden Dummy to do so. If you want to test it out in a comp battle, click on the Arena Guardian statue to do so.
When testing a hero, the hero will appear in the second slot with Ulric in the first slot. If you are testing a different hero, the hero will appear in the first slots with two Ulrics in the first and the second slot.
The Ulrics will be equal to the level of your hero and will only use the basic attacks of their abilities. The Ulrics will also regenerate health and gain very high defense when on low HP making them practically immortal. When testing, two Hypogean Elites will spawn in their respective positions and 1 Hypogean Mage will spawn in the fourth position. These enemies are also equal to their level and will only use their regular attack. However, the enemy still retains the faction bonus for having 3 Hypogeans whereas you will only get the bonus if you have 3 Lightbearer heroes onscreen. After an Hypogean is defeated another one will spawn. You can watch as your selected hero attack against the enemies and see their abilities of each of their skills. Although hero testing is very useful, it often makes that the heroes look much stronger than they are. An example of this is Baden. When testing Baden, he will have an army of shadow minions on screen that almost instantly kill any enemy this is because of how quickly your hero will get energy as they will get the bonus energy from kills so you have to factor that into the test.
Players can also fight with the Arena Guardian where you can test the selected hero along with any other heroes you unlocked. The enemy comp will vary for every heroes in the game and you will need to put other heroes on your lineup to defeat the opposing side.