Add more test cases in the multi-frame integration test

The tests are in a response to an issue found when frames get added/removed in quick succession. It was due to the timing of the debounce used in FrameObserver.
This also works to test against possible edge cases and ensures robustness of the feature by going full circle.

src/annotator/test/integration/multi-frame-test.js

 'use strict';
 
 var proxyquire = require('proxyquire');
-var isLoaded = require('../../util/frame-util.js').isLoaded;
+var isLoaded = require('../../util/frame-util').isLoaded;
+
+var FRAME_ADD_WAIT = require('../../frame-observer').DEBOUNCE_WAIT + 10;
 
 describe('CrossFrame multi-frame scenario', function () {
   var fakeAnnotationSync;
@@ -143,7 +145,7 @@ describe('CrossFrame multi-frame scenario', function () {
             'expected dynamically added frame to be modified');
           resolve();
         });
-      }, 0);
+      }, FRAME_ADD_WAIT);
     });
   });
 
@@ -169,4 +171,75 @@ describe('CrossFrame multi-frame scenario', function () {
     });
   });
 
+  it('detects a frame dynamically removed, and added again', function () {
+    // Create a frame before initializing
+    var frame = document.createElement('iframe');
+    container.appendChild(frame);
+
+    // Now initialize
+    crossFrame.pluginInit();
+
+    return new Promise(function (resolve) {
+
+      isLoaded(frame, function () {
+        assert(frame.contentDocument.body.hasChildNodes(),
+          'expected initial frame to be modified');
+
+        frame.remove();
+
+        // Yield to let the DOM and CrossFrame catch up
+        setTimeout(function () {
+          // Add the frame again
+          container.appendChild(frame);
+
+          // Yield again
+          setTimeout(function () {
+            isLoaded(frame, function () {
+              assert(frame.contentDocument.body.hasChildNodes(),
+                'expected dynamically added frame to be modified');
+              resolve();
+            });
+          }, FRAME_ADD_WAIT);
+        }, 0);
+      });
+    });
+  });
+
+  it('detects a frame dynamically added, removed, and added again', function () {
+
+    // Initialize with no initial frame
+    crossFrame.pluginInit();
+
+    // Add a frame to the DOM
+    var frame = document.createElement('iframe');
+    container.appendChild(frame);
+
+    return new Promise(function (resolve) {
+      // Yield to let the DOM and CrossFrame catch up
+      setTimeout(function () {
+        isLoaded(frame, function () {
+          assert(frame.contentDocument.body.hasChildNodes(),
+            'expected dynamically added frame to be modified');
+
+          frame.remove();
+
+          // Yield again
+          setTimeout(function () {
+            // Add the frame again
+            container.appendChild(frame);
+
+            // Yield
+            setTimeout(function () {
+              isLoaded(frame, function () {
+                assert(frame.contentDocument.body.hasChildNodes(),
+                  'expected dynamically added frame to be modified');
+                resolve();
+              });
+            }, FRAME_ADD_WAIT);
+          }, 0);
+        });
+      }, FRAME_ADD_WAIT);
+    });
+  });
+
 });
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