This test ensures that getImageData works correctly.
PASS: pixel at (0,0) was [0,0,0,255]
PASS: pixel at (4,0) was [0,11,0,255]
PASS: pixel at (8,0) was [0,21,0,255]
PASS: pixel at (12,0) was [0,32,0,255]
PASS: pixel at (16,0) was [0,43,0,255]
PASS: pixel at (20,0) was [0,53,0,255]
PASS: pixel at (24,0) was [0,64,0,255]
PASS: pixel at (28,0) was [0,74,0,255]
PASS: pixel at (32,0) was [0,85,0,255]
PASS: pixel at (36,0) was [0,96,0,255]
PASS: pixel at (40,0) was [0,106,0,255]
PASS: pixel at (44,0) was [0,117,0,255]
PASS: pixel at (48,0) was [0,128,0,255]
PASS: pixel at (52,0) was [0,138,0,255]
PASS: pixel at (56,0) was [0,149,0,255]
PASS: pixel at (60,0) was [0,159,0,255]
PASS: pixel at (64,0) was [0,170,0,255]
PASS: pixel at (68,0) was [0,181,0,255]
PASS: pixel at (72,0) was [0,191,0,255]
PASS: pixel at (76,0) was [0,202,0,255]
PASS: pixel at (80,0) was [0,213,0,255]
PASS: pixel at (84,0) was [0,223,0,255]
PASS: pixel at (88,0) was [0,234,0,255]
PASS: pixel at (92,0) was [0,244,0,255]
PASS: pixel at (96,0) was [0,255,0,255]
PASS: pixel at (5,5) was [64,128,191,255]
PASS: Correctly retrieved every pixel in a row
PASS: Correct data for content outside canvas bounds