chromium/src/third_party/blink/web_tests/fast/canvas/canvas-arc-zero-lineto.html

<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<canvas id="canvas" width="100" height="100"></canvas>

<script>
function shouldBeBlackPixel(ctx, x, y)
{
    var data = ctx.getImageData(x, y, 1, 1).data;
    assert_equals(data[0], 0);
    assert_equals(data[1], 0);
    assert_equals(data[2], 0);
    assert_equals(data[3], 255);
}

test(function(t) {
    var ctx = document.getElementById('canvas').getContext('2d');
    ctx.lineWidth = 4;
    
    // moveTo + empty arc (swing == 0)
    ctx.beginPath();
    ctx.moveTo(20, 20);
    ctx.arc(80, 30, 10, -Math.PI/2, -Math.PI/2, true);
    ctx.stroke();
    shouldBeBlackPixel(ctx, 50, 20);
    
    // moveTo + empty arc (radius == 0)
    ctx.beginPath();
    ctx.moveTo(20, 40);
    ctx.arc(80, 40, 0, 0, 6, false);
    ctx.stroke();
    shouldBeBlackPixel(ctx, 50, 40)
    
    // empty arc (swing == 0) + lineTo
    ctx.beginPath();
    ctx.arc(20, 50, 10, Math.PI/2, Math.PI/2, false);
    ctx.lineTo(80, 60);
    ctx.stroke();
    shouldBeBlackPixel(ctx, 50, 60);
    
    // empty arc (radius == 0) + lineTo
    ctx.beginPath();
    ctx.arc(20, 80, 0, 0, 6, false);
    ctx.lineTo(80, 80);
    ctx.stroke();
    shouldBeBlackPixel(ctx, 50, 80);
}, 'Series of tests to ensure zero-length arc extends current subpath (bug 55696)');
</script>