diff --git a/platform/features/layout/src/LayoutSelection.js b/platform/features/layout/src/LayoutSelection.js
index 0398d3d308..bb1574f0ff 100644
--- a/platform/features/layout/src/LayoutSelection.js
+++ b/platform/features/layout/src/LayoutSelection.js
@@ -7,6 +7,12 @@ define(
 
         /**
          * Tracks selection state for Layout and Fixed Position views.
+         * This manages and mutates the provided selection array in-place,
+         * and takes care to only modify the array elements it manages
+         * (the view's proxy, and the single selection); selections may be
+         * added or removed elsewhere provided that similar care is taken
+         * elsewhere.
+         *
          * @param {Array} selection the selection array from the view's scope
          * @param [proxy] an object which represents the selection of the view
          *        itself (which handles view-level toolbar behavior)
diff --git a/platform/features/layout/test/LayoutSelectionSpec.js b/platform/features/layout/test/LayoutSelectionSpec.js
index 54742a0531..3712afec3f 100644
--- a/platform/features/layout/test/LayoutSelectionSpec.js
+++ b/platform/features/layout/test/LayoutSelectionSpec.js
@@ -6,6 +6,79 @@ define(
         "use strict";
 
         describe("Layout/fixed position selection manager", function () {
+            var testSelection,
+                testProxy,
+                testElement,
+                otherElement,
+                selection;
+
+            beforeEach(function () {
+                testSelection = [];
+                testProxy = { someKey: "some value" };
+                testElement = { someOtherKey: "some other value" };
+                otherElement = { yetAnotherKey: 42 };
+                selection = new LayoutSelection(testSelection, testProxy);
+            });
+
+            it("adds the proxy to the selection array", function () {
+                expect(testSelection).toEqual([testProxy]);
+            });
+
+            it("includes selected objects alongside the proxy", function () {
+                selection.select(testElement);
+                expect(testSelection).toEqual([testProxy, testElement]);
+            });
+
+            it("allows elements to be deselected", function () {
+                selection.select(testElement);
+                selection.deselect();
+                expect(testSelection).toEqual([testProxy]);
+            });
+
+            it("replaces old selections with new ones", function () {
+                selection.select(testElement);
+                selection.select(otherElement);
+                expect(testSelection).toEqual([testProxy, otherElement]);
+            });
+
+            it("allows retrieval of the current selection", function () {
+                selection.select(testElement);
+                expect(selection.get()).toBe(testElement);
+                selection.select(otherElement);
+                expect(selection.get()).toBe(otherElement);
+            });
+
+            it("can check if an element is selected", function () {
+                selection.select(testElement);
+                expect(selection.selected(testElement)).toBeTruthy();
+                expect(selection.selected(otherElement)).toBeFalsy();
+                selection.select(otherElement);
+                expect(selection.selected(testElement)).toBeFalsy();
+                expect(selection.selected(otherElement)).toBeTruthy();
+            });
+
+            it("cleans up the selection on destroy", function () {
+                selection.destroy();
+                expect(testSelection).toEqual([]);
+            });
+
+            it("preserves other elements in the array", function () {
+                testSelection.push(42);
+                selection.select(testElement);
+                expect(testSelection).toEqual([testProxy, testElement, 42]);
+            });
+
+            it("considers the proxy to be selected", function () {
+                expect(selection.selected(testProxy)).toBeTruthy();
+                selection.select(testElement);
+                // Even when something else is selected...
+                expect(selection.selected(testProxy)).toBeTruthy();
+            });
+
+            it("treats selection of the proxy as a no-op", function () {
+                selection.select(testProxy);
+                expect(testSelection).toEqual([testProxy]);
+            });
 
         });
     }