anchor.diff:    test('fillStyle', () {
       context.fillStyle = "red";
       context.fillRect(0, 0, canvas.width, canvas.height);
  -    expect(readPixel(), [255, 0, 0, 255]);
  +    checkPixel(readPixel(), [255, 0, 0, 255]);
     });
   
     test('strokeStyle', () {
  
positive.code: 
  // Some rounding errors in the browsers.
  checkPixel(List<int> pixel, List<int> expected) {
    expect(pixel[0], closeTo(expected[0], 1));
    expect(pixel[1], closeTo(expected[1], 1));
    expect(pixel[2], closeTo(expected[2], 1));
    expect(pixel[3], closeTo(expected[3], 1));
  }
  
  main() {
  
negative.code:   test('setFillColorHsl hue', () {
      context.setFillColorHsl(0, 100, 50);
      context.fillRect(0, 0, canvas.width, canvas.height);
      checkPixel(readPixel(), [255, 0, 0, 255]);
    });
  
    test('setFillColorHsl hue 2', () {
      context.setFillColorHsl(240, 100, 50);
      context.fillRect(0, 0, canvas.width, canvas.height);
      checkPixel(readPixel(), [0, 0, 255, 255]);
    });
  
    test('setFillColorHsl sat', () {
  