Test that an invalid xlink:href on a 'pattern' element has no effect on the pattern, and that the pattern isn't rendered since the default 'width' and 'height' is 0. A subtest that explicitly specifies 'width' and 'height' as 0 is added as a reference. Both of these cases should result in the fallback color being used.
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The test is passed if there is a green rectangle visible on the page, and no red.