[Plot] Add specs for PlotPanZoomStackGroup

Add specs to verify the behavior of PlotPanZoomStackGroup,
which is responsible for synchronizing the domain axis
between multiple sub-plots in a stacked plot view.
WTD-625.

platform/features/plot/src/elements/PlotPanZoomStackGroup.js

@@ -38,7 +38,7 @@ define(
 
             function clearPanZoom() {
                 stacks.forEach(function (stack) {
-                    stack.popPanZoom();
+                    stack.clearPanZoom();
                 });
             }
 

platform/features/plot/test/elements/PlotPanZoomStackGroupSpec.js

@@ -5,10 +5,103 @@
  */
 define(
     ["../../src/elements/PlotPanZoomStackGroup"],
-    function (PlotController) {
+    function (PlotPanZoomStackGroup) {
         "use strict";
 
+        var COUNT = 8;
+
         describe("A plot pan-zoom stack group", function () {
+            var stacks,
+                group;
+
+            beforeEach(function () {
+                group = new PlotPanZoomStackGroup(COUNT);
+                stacks = [];
+                while (stacks.length < COUNT) {
+                    stacks.push(group.getPanZoomStack(stacks.length));
+                }
+            });
+
+            it("creates a number of separate stacks", function () {
+                expect(group.getPanZoomStack(0)).toBeDefined();
+                expect(group.getPanZoomStack(COUNT - 1)).toBeDefined();
+                expect(group.getPanZoomStack(COUNT)).toBeUndefined();
+            });
+
+            it("synchronizes pan-zoom stack depth", function () {
+                expect(group.getDepth()).toEqual(1);
+                group.getPanZoomStack(1).pushPanZoom([ 10, 20 ], [ 30, 40 ]);
+                stacks.forEach(function (stack) {
+                    expect(stack.getDepth()).toEqual(2);
+                });
+            });
+
+            it("synchronizes domain but not range", function () {
+                // Set up different initial states
+                stacks.forEach(function (stack, i) {
+                    stack.pushPanZoom([ i, i ], [ i, i ]);
+                });
+
+                // Push a new pan-zoom state onto one of the stacks
+                group.getPanZoomStack(1).pushPanZoom([ 99, 99 ], [ 42, 42 ]);
+
+                // Should changed domain values for all stacks, but
+                // only changed range values for stack 1
+                stacks.forEach(function (stack, i) {
+                    expect(stack.getOrigin())
+                        .toEqual([99, i === 1 ? 99 : i]);
+                    expect(stack.getDimensions())
+                        .toEqual([42, i === 1 ? 42 : i]);
+                });
+            });
+
+            it("synchronizes base pan-zoom", function () {
+                group.setBasePanZoom([10, 9], [8, 7]);
+                stacks.forEach(function (stack) {
+                    expect(stack.getOrigin()).toEqual([10, 9]);
+                    expect(stack.getDimensions()).toEqual([8, 7]);
+                });
+            });
+
+            it("clears pan-zoom on request", function () {
+                // Set up different initial states
+                stacks.forEach(function (stack, i) {
+                    stack.pushPanZoom([ i, i ], [ i, i ]);
+                });
+
+                // Verify that we have a greater depth
+                expect(group.getDepth() > 1).toBeTruthy();
+
+                // Clear the pan-zoom state
+                group.clearPanZoom();
+
+                // Should be back down to our initial state
+                expect(group.getDepth()).toEqual(1);
+                stacks.forEach(function (stack) {
+                    expect(stack.getDepth()).toEqual(1);
+                });
+            });
+
+            it("pops pan-zoom on request", function () {
+                // Set up different initial states
+                stacks.forEach(function (stack, i) {
+                    stack.pushPanZoom([ i, i ], [ i, i ]);
+                });
+
+                // Verify that we have a greater depth
+                expect(group.getDepth()).toEqual(COUNT + 1);
+
+                // Clear the pan-zoom state
+                group.popPanZoom();
+
+                // Should be back down to our initial state
+                expect(group.getDepth()).toEqual(COUNT);
+                stacks.forEach(function (stack) {
+                    expect(stack.getDepth()).toEqual(COUNT);
+                });
+            });
+
+
         });
     }
 );