Tests: Moved issue test #4284 to unit-tests.

samples/unit-tests/series-column/update/demo.js

@@ -0,0 +1,30 @@
+QUnit.test('Column update(#4284)', function (assert) {
+    var chart = $('#container').highcharts({
+        chart: {
+            animation: false
+        },
+
+        xAxis: {
+            categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
+                'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
+        },
+
+        series: [{
+            type: 'column',
+            animation: false,
+            data: [29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4]
+        }]
+
+    }).highcharts();
+
+    var point = chart.series[0].points[0];
+    point.update({ y: 100 });
+
+
+    assert.notEqual(
+        point.graphic.element.getAttribute('visibility'),
+        'hidden',
+        'Point is visible'
+    );
+
+});