Series of tests to ensure correct behaviour on negative source/destination of a HTMLCanvasElement On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS imgdata[4] is 0 PASS imgdata[5] is 255 PASS imgdata[6] is 0 FAIL imgdata[0] should be 255. Was 0. PASS imgdata[1] is 0 FAIL imgdata[2] should be 0. Was 255. PASS imgdata[4] is 0 PASS imgdata[5] is 0 PASS imgdata[6] is 0 PASS successfullyParsed is true TEST COMPLETE