Updated controller.scatter.test.js to test default tooltip callbacks

- This moves the mouse over the drawn point and verifies that there is
  no title in the tooltip and that the body contains expected content.

test/specs/controller.scatter.test.js

@@ -3,6 +3,43 @@ describe('Chart.controllers.scatter', function() {
 		expect(typeof Chart.controllers.scatter).toBe('function');
 	});
 
+	it('should test default tooltip callbacks', function() {
+		var chart = window.acquireChart({
+			type: 'scatter',
+			data: {
+				datasets: [{
+					data: [{
+						x: 10,
+						y: 15
+					}],
+					label: 'dataset1'
+				}],
+			},
+			options: {}
+		});
+		var meta = chart.getDatasetMeta(0);
+		var point = meta.data[0];
+		var node = chart.canvas;
+		var rect = node.getBoundingClientRect();
+		var evt = new MouseEvent('mousemove', {
+			view: window,
+			bubbles: true,
+			cancelable: true,
+			clientX: rect.left + point._model.x,
+			clientY: rect.top + point._model.y,
+		});
+
+		// Manually trigger rather than having an async test
+		node.dispatchEvent(evt);
+
+		// Check and see if tooltip was displayed
+		var tooltip = chart.tooltip;
+
+		// Title should be empty
+		expect(tooltip._view.title.length).toBe(0);
+		expect(tooltip._view.body[0].lines).toEqual(['(10, 15)']);
+	});
+
 	describe('showLines option', function() {
 		it('should not draw a line if undefined', function() {
 			var chart = window.acquireChart({