Go straight ahead through the entrance door. There's some blue gel falling from above. There's also some water falling from a different pipe. Across from the entrance door, up in the wall, there is a red button.
Put a portal under the spot where the blue gel is falling. Put a portal of the other color in front of where the red button is. Before the gel can fall back through the portal, move that portal somewhere else. This will make repulsion gel land on the floor in front of the red button.
Now look to the left of the entrance door. There is a white wall over there. Create a portal on it such that the blue gel comes out of it. The blue gel will hit the same spot where the water is pouring down, preventing the blue gel from sticking to the floor.
Leave the portals as they are and bounce on the blue gel to press the red button. This stops the flow of water for a few seconds, allowing some blue gel to stick to the floor. Bounce on that gel to the ledge above. Turn left and go through the exit door.
In this next area, put a portal on the angled piece of wall, and put a portal of the other color on the spot that the gel is falling on.
Now look to the side of the room where there are some white walls up high. Make a portal on one of those, then another on the wall nearby. Go through. You should be standing on a ledge high up from the floor. Create a portal below you, then a portal of the other color on the angled wall. Fall into the portal and you should be thrown against the wall that you put repulsion gel on just a moment ago. This will bounce you out through the exit.
You will need some repulsion gel for this next part. You can look down and see the testing area that you just left, so put a portal on the spot that the gel is hitting.
There are some stairs in this area. Go up. Go to the edge where there is kind of a cage. There is a white wall up above, in the distance. Put a portal on that such that the gel comes out from it. This should put blue gel on the angled metal vent across from the portal.
There is a white floor down below. Put a portal on that such that you will come out from that high wall in the distance that you just sent some gel through. Drop into that hole and you should be thrown onto the blue gel on the angled piece of metal and end up on a walkway.
Around the side, there are couple of white areas on the walls. Put a portal on each of these parts, making sure that the upper portal is as high up on the wall as you can put it. Go through, jumping to the metal walkway across from the upper portal.
Now go up the stairs to the next test chamber.