This test has a gradient with gradientUnits='objectBoundingBox' which is a fade from black to white.
The gradient is used for the stroke of a line. Lines don't have a boundingbox, since they are one-dimensional, even though the
stroke-width makes it look like they should have a boundingbox with non-zero width and height.
See the coordinate chapter, last paragraph of 7.11.
The left rectangle has four 'line' elements rotated in different ways. The right rectangle has four 'rect' elements
rotated in the same way as the 'line' elements. Both of these rectangles and their contents should look the same
for the test to pass; all lines are solid black except for the diagonal from bottom left to top right, which has a black to white gradient.
