There are two testing systems within the Inner Tower: the current system designed for Regulars and the ancient system designed for Irregulars. The current testing system was likely implemented after Zahard, the 10 Great Warriors and his helpers had conquered the first 134 Floors of the Tower.
Current Testing System
When a Regular is climbing the Tower, he or she has to pass one or more tests on each Floor. The tests are created to determine whether the Regular is worthy of going to the next Floor. Generally, the difficulty increases the higher one climbs. There are however a few exceptions, like the 2nd Floor and the 20th Floor, where the difficulty is particularly high.
The tests can be given to the Regulars by either the Guardian of the Floor or, more often, by the Guardian's proxy, the Floor's Ruler. Each examination at each Floor given to Regulars is usually coordinated by the Test Director and the Test Administrators under their command since they represent the Floor's Ruler. However at special occasions the Guardian of the Floor will give the test.
Each Floor's Ruler and their subordinates have the right to decide nature of the exam, as long as they follow the Guardian's wishes. However if the Guardian raises objections, the Ruler must follow the Guardian's wish. These exams are then taken by future test takers, politically named as Regulars.
To be considered worthy of taking the next test, each Regular must pass all the previous tests. They may only be excluded from taking certain tests if they've "passed early". Apparently, there are special tests which allow exceptionally strong individuals to skip a certain number of Floors.
From the 3rd Floor and onwards, even if a Regular fails, they have the right to retake the tests. Most or all tests on a Floor are compulsory and you need to pass a test to proceed to the next. This means if a Regular passes the first test but fails the second test, they fail the Floor. They have the right to retake the Floor but they must start all over again. This is why Yeon Yihwa and Ja Wangnan were stuck on the 20th Floor as they had to go through the first test and also take the other tests. From the 30th Floor onwards there's only one chance to take and pass tests per year.
The Guardian's Tests
This is an actual fact, the original testing system was designed to test an Irregular. The tests might have involved battling Shinheuh.
Note: For now, it is too early to assume Zahard and the 10 Great Warriors underwent gruelling challenges all the time. It is unknown how the Irregular's Tests were conducted during their time.
Note #2: These days, an Irregular can choose to take a Guardian's Testing system or they can take part in the Regular Testing system.
After entering the Tower, an Irregular is then teleported to the First Floor of the Inner Tower to take the Guardian's test (conducted by Headon). And only an Irregular can request to take a Guardian's test. Take note that one cannot become a "chosen one" or an Irregular by participating in the Guardian's test, like Baam or Rachel's group in the Submerged Fish Hunt Test. The Guardian's test itself is bound by a set of the Tower's Rules.
The Guardian's test reflects the "worth of the things", the Irregular wishes to gain from the Tower and in essence, their desires. When the Irregular passes a Guardian's test, it is possible the Guardian may fulfill part or all of their wishes expressed before the test. The Irregular will then be teleported to the next Floor, It is unknown if Irregulars who fail to pass a Guardian's test are allowed to retake it or are promptly disqualified from climbing the Tower.
Tests that have been shown in Tower of God
- Irregular's Test (may include the Ball Test)
- "Deathmatch" Test
- Lero-Ro's test
- Door Test
- Crown Game (A bonus game)
- Position Test
- Submerged Fish Hunt Test (A Guardian's Test)
- Survival Round
- World's Strongest Regular
- The Trustworthy Room (A bonus game made to find a team for Viole)
- Flower of Zygaena (This was actually a ruse by the Rankers to try and get the flower back from Urek Mazino)
- A test where one team has to get a key into a box, signalling their win. The exact rules were unknown.
- Battle of Cannons: A test conducted in trenches, where one team has to disable the other team's cannons, which lie at opposite ends of the field.
No tests because the Guardian is dead.
Tests in the Tower also include certain special tests. These tests may or may not assist in further progress in climbing the Tower, but may also carry other kinds of benefits.
Known examples of these kinds of tests:
- The Wonsulsa test taken at the Research Association. Taking this test makes one a certified Wonsul user.
- Iron Man - this is a special contract that only members of the Mule Family can obtain and to do so the family had to take a special test from an unspecified Guardian.
- The two mole like drawings under Lero-Ro's eyes, these symbolize that he has passed a special test (what kind of test is unknown although it was most likely to become a Jeonsulsa).
- The Hell Express taken on the 35th Floor. It is a test that enables Regulars to quickly travel to the 43rd Floor. However, due to its extreme difficulty, not many Regulars survive until the end.