Test that the viewer can handle the xlink:href attribute on linear gradients. The top rectangle has a simple blue (left) to lime (right) linear gradient. The lower one has a different gradient definition, but should look the same as the one above, because the gradient makes a reference to the first gradient, without modifying any attribute.
Run the test. No interaction required.
The test is passed if there are two rectangles, both with a blue to lime gradient.