The computer promises that cake and grief counseling will be available at the end of the test. Sounds... terrifying?
After you go through the entry hallway and get into the first 'room' of the chamber, look above the hallway entrance. There is a piece of wall sticking out above there. Make a portal on it. Then, look at the floor and make a portal of the other color below you. While you fall, look down and make a new portal where you are about to land, the same color as the one you put on the floor. If you do it correctly, your increased momentum will take you through the particle field above the glass wall.
In the next 'room', put a portal on the black spot on the wall where the pellet is hitting it. Note that if you go through a particle field, any portals that you have placed will disappear. So, make a portal of the other color facing the other particle field. Once the pellet goes through, walk through the particle field that has the containment thing behind it. Quickly make a portal above the containment thing, and then make another portal where the pellet is now bouncing inside of this shielded area. When the pellet goes through, it will go into the containment thing.
Take the platform to the next area. As with the first 'room', there is a piece of wall sticking out above the entrance, and a floor that you can put portals on. However, as you will find out if you try, falling through a floor portal to get through a portal on the piece of wall sticking out doesn't give you enough momentum to reach the floor portal again. But there is a small side room where there is a pit.
So, make a portal on the piece of wall sticking out above the entrance, then go to the side room and make a portal of a different color on the floor of the pit. Fall into it, and then as soon as you start falling, look straight down and make another floor portal so you can get enough momentum to go over the glass wall. If you still don't make it, just keep making floor portals under you as you fall.
In this next room, make a portal on the piece of wall sticking out, then another on the floor. This time, you get enough momentum to land on the floor again, so just make another floor portal as you fall to get over the barrier.
Finally, make a portal on the wall where the pellet hits (you can make the portal on the angled piece of wall or on the room wall itself.) Then make a portal on the wall facing the other angled piece (not on the angled part itself). If done successfully, the pellet will go into the containment thing.
Once that's done, you'll have to do the old wall portal to floor portal trick to get the momentum to get back to the area that has the pellet shooter and the pellet containment unit.
In that area, there is now an open door in which you can see some moving platforms. Shoot a portal onto the far wall that you can see, then make a portal on a wall in the room you're in. Look through the portal to see the approaching platforms, and step onto the platform when it appears. Then, shoot a portal onto the next far wall that you can see and ride the platform back into the entrance to the big room. Hop off of the platform before it disappears and make a portal of the other color to see the approaching platforms. Get onto a platform and shoot a portal into the room that you can see in the distance.
Notice the piece of wall sticking out. After pressing a couple of buttons, you will want to put a portal onto it, and then put a portal of the other color onto the floor where the containment unit is shining its light. But first, you need to take care of those buttons. Here's how. Ride a platform up to one of the rooms near the ceiling. Go in, then make a portal on the wall near the button here. Next, look out of the room to the other room, and shoot a portal of the other color in that far room. Finally, press the button in the room that you're in, then go through the portal and press the button in the other room. Then put a portal onto the piece of wall that sticks out, and finally another one on the floor under the containment thing.
If you did it correctly, the pellet will go into the containment thing, and you can ride the platform to the elevator.