Notes:

The player, playing as Chell, is walking on a Hard Light Bridge, which is made from sunlight pumped down from the surface, into Aperture Science. (As explained by GLaDOS at the beginning of the test.) You need to use it to get to the other side, as you're unable to just portal over there and actually get to the elevator, as you need to use the Hard Light Bridge to catch a Weighted Storage Cube before it falls into the acid below, (which'll kill you if you fall in for more than about ten seconds,) and is supposedly fizzled, or, as very few call it, emancipated, and place it on a button, which opens the door to the elevator, which leads you to the next test.
This is in Chapter 3: The Return, and, this is Test Chamber 11.
https://i1.theportalwiki.net/img/thumb/6/62/Portal_2_Chapter_3_Test_Chamber_11.png/264px-Portal_2_Chapter_3_Test_Chamber_11.png
https://i1.theportalwiki.net/img/thumb/8/84/Portal_2_Chapter_3_Test_Chamber_11_overview.png/800px-Portal_2_Chapter_3_Test_Chamber_11_overview.png
It's the first test to involve Hard Light Bridges, and earns you the achievement "Bridge Over Troubling Water (Complete the first Hard Light Bridge test)".
It includes a Rat Man den.
v=VnhDd29XpCohttps://i1.theportalwiki.net/img/thumb/0/08/Portal_2_Chapter_3_Test_Chamber_11_den.png/800px-Portal_2_Chapter_3_Test_Chamber_11_den.png
Wheatley makes a brief appearance behind this panel, letting the players who see him know that he's Still Alive.
https://www.youtube.com/watch?v=VnhDd29XpCo

https://theportalwiki.com/wiki/Portal_2_Chapter_3_Test_Chamber_11