Test passes if:
1. the rectangle 1, 2, 3 show up in a row in a red rectangle.
2. the rectangle 1, 2, 3 are distributed such that the empty space between any two adjacent rectangle is the same, and the empty space of the row before the first and after the last rectangle are half the size of the other empty spaces.
3. the height of the 1, 2, 3 is the same as the height of the red rectangle.