Fix cached JPEG test

This test didn't really check anything useful as the end result would be
the same if the second JPEG failed to render.

Fix this by clearing the canvas between the images, so we can tell if
the second image actually rendered or not.

diff --git a/tests/test.jpeg.js b/tests/test.jpeg.js
index 6834f03d4ea3a0d564b7ae539bc008edb0e6862f..7580c617163a700ff59eb2ff97dbcbd20d6c5046 100644 (file)
--- a/tests/test.jpeg.js
+++ b/tests/test.jpeg.js
@@ -246,6 +246,8 @@ describe('JPEG Decoder', function () {
 
         testDecodeRect(decoder, 0, 0, 4, 4, data1, display, 24);
 
+        display.fillRect(0, 0, 4, 4, [128, 128, 128, 255]);
+
         let data2 = [
             // JPEG data
             0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46,