The test passes if the rendering of the three rectangles matches those
in the reference image. Specifically:
The upper rectangle is filled with an elliptical radial gradient
with blue at the center and lime at its edges.
The middle rectangle is also filled with an elliptical radial
gradient with blue inside and lime outside, but with the center
point of the gradient in the top-left quadrant of the rectangle.
The bottom rectangle is filled with a circular radial gradient
with yellow at the center and blue at its edges. Since it is circular,
most of the rectangle is filled with plain blue.
