diff --git a/src/testUtils/__tests__/stub_browser_storage.js b/src/testUtils/__tests__/stub_browser_storage.js
new file mode 100644
index 0000000000000..83e4a7440ddd3
--- /dev/null
+++ b/src/testUtils/__tests__/stub_browser_storage.js
@@ -0,0 +1,85 @@
+import expect from 'expect.js';
+
+import StubBrowserStorage from '../stub_browser_storage';
+
+describe('StubBrowserStorage', () => {
+  describe('#getItem() / #setItem()', () => {
+    it('stores items as strings', () => {
+      const store = new StubBrowserStorage();
+      store.setItem(1, 1);
+      expect(store.getItem(1)).to.be('1');
+    });
+
+    it('stores keys as strings', () => {
+      const store = new StubBrowserStorage();
+      store.setItem(1, 1);
+      expect(store.key(0)).to.be('1');
+    });
+
+    it('returns null for missing keys', () => {
+      const store = new StubBrowserStorage();
+      expect(store.getItem('unknown key')).to.be(null);
+    });
+  });
+
+  describe('#length', () => {
+    it('reports the number of items stored', () => {
+      const store = new StubBrowserStorage();
+      store.setItem(1, 1);
+      store.setItem(2, 2);
+      store.setItem(3, 3);
+      store.setItem(4, 4);
+      expect(store).to.have.length(4);
+    });
+
+    it('does not trip on items getting reset', () => {
+      const store = new StubBrowserStorage();
+      store.setItem(1, 1);
+      store.setItem(1, 2);
+      expect(store).to.have.length(1);
+    });
+  });
+
+  describe('#key()', () => {
+    it('returns the key as a specific index', () => {
+      const store = new StubBrowserStorage();
+      store.setItem(1, 2);
+      expect(store.key(0)).to.be('1');
+      expect(store.key(1)).to.be(undefined);
+    });
+  });
+
+  describe('size limiting', () => {
+    it('allows limiting the storage size', () => {
+      const store = new StubBrowserStorage();
+      store._setSizeLimit(10);
+      store.setItem('abc', 'def'); // store size is 6, key.length + val.length
+      expect(() => {
+        store.setItem('ghi', 'jkl');
+      }).throwError(/quota/);
+    });
+
+    it('allows defining the limit as infinity', () => {
+      const store = new StubBrowserStorage();
+      store._setSizeLimit(Infinity);
+      store.setItem('abc', 'def');
+      store.setItem('ghi', 'jkl'); // unlike the previous test, this doesn't throw
+    });
+
+    it('requires setting the limit before keys', () => {
+      const store = new StubBrowserStorage();
+      store.setItem('key', 'val');
+      expect(() => {
+        store._setSizeLimit(10);
+      }).throwError(/before setting/);
+    });
+
+    it('respects removed items', () => {
+      const store = new StubBrowserStorage();
+      store._setSizeLimit(10);
+      store.setItem('abc', 'def');
+      store.removeItem('abc');
+      store.setItem('ghi', 'jkl'); // unlike the previous test, this doesn't throw
+    });
+  });
+});
diff --git a/src/testUtils/stub_browser_storage.js b/src/testUtils/stub_browser_storage.js
new file mode 100644
index 0000000000000..cf628e0eca515
--- /dev/null
+++ b/src/testUtils/stub_browser_storage.js
@@ -0,0 +1,92 @@
+const keys = Symbol('keys');
+const values = Symbol('values');
+const remainingSize = Symbol('remainingSize');
+
+export default class StubBrowserStorage {
+  constructor() {
+    this[keys] = [];
+    this[values] = [];
+    this[remainingSize] = 5000000; // 5mb, minimum browser storage size
+  }
+
+  get length() {
+    return this[keys].length;
+  }
+
+  key(i) {
+    return this[keys][i];
+  }
+
+  getItem(key) {
+    key = String(key);
+
+    const i = this[keys].indexOf(key);
+    if (i === -1) return null;
+    return this[values][i];
+  }
+
+  setItem(key, value) {
+    key = String(key);
+    value = String(value);
+    this._takeUpSpace(this._calcSizeOfAdd(key, value));
+
+    const i = this[keys].indexOf(key);
+    if (i === -1) {
+      this[keys].push(key);
+      this[values].push(value);
+    } else {
+      this[values][i] = value;
+    }
+  }
+
+  removeItem(key) {
+    key = String(key);
+    this._takeUpSpace(this._calcSizeOfRemove(key));
+
+    const i = this[keys].indexOf(key);
+    if (i === -1) return;
+    this[keys].splice(i, 1);
+    this[values].splice(i, 1);
+  }
+
+  // non-standard api methods
+  _getKeys() {
+    return this[keys].slice();
+  }
+
+  _getValues() {
+    return this[values].slice();
+  }
+
+  _setSizeLimit(limit) {
+    if (this[keys].length) {
+      throw new Error('You must call _setSizeLimit() before setting any values');
+    }
+
+    this[remainingSize] = limit;
+  }
+
+  _calcSizeOfAdd(key, value) {
+    const i = this[keys].indexOf(key);
+    if (i === -1) {
+      return key.length + value.length;
+    }
+    return value.length - this[values][i].length;
+  }
+
+  _calcSizeOfRemove(key) {
+    const i = this[keys].indexOf(key);
+    if (i === -1) {
+      return 0;
+    }
+    return 0 - (key.length + this[values][i].length);
+  }
+
+  _takeUpSpace(delta) {
+    if (this[remainingSize] - delta < 0) {
+      throw new Error('something about quota exceeded, browsers are not consistent here');
+    }
+
+    this[remainingSize] -= delta;
+  }
+}
diff --git a/src/ui/public/chrome/__tests__/Tab.js b/src/ui/public/chrome/__tests__/Tab.js
index b25995730ec20..c83b1a5a6cbf0 100644
--- a/src/ui/public/chrome/__tests__/Tab.js
+++ b/src/ui/public/chrome/__tests__/Tab.js
@@ -1,6 +1,6 @@
 const Tab = require('../Tab');
 const expect = require('expect.js');
-const TabFakeStore = require('./_TabFakeStore');
+const StubBrowserStorage = require('testUtils/stub_browser_storage');
 
 describe('Chrome Tab', function () {
   describe('construction', function () {
@@ -87,7 +87,7 @@ describe('Chrome Tab', function () {
     });
 
     it('discovers the lastUrl', function () {
-      const lastUrlStore = new TabFakeStore();
+      const lastUrlStore = new StubBrowserStorage();
       const tab = new Tab({ id: 'foo', lastUrlStore });
       expect(tab.lastUrl).to.not.equal('bar');
 
@@ -102,7 +102,7 @@ describe('Chrome Tab', function () {
 
   describe('#setLastUrl()', function () {
     it('updates the lastUrl and storage value if passed a lastUrlStore', function () {
-      const lastUrlStore = new TabFakeStore();
+      const lastUrlStore = new StubBrowserStorage();
       const tab = new Tab({ id: 'foo', lastUrlStore });
 
       expect(tab.lastUrl).to.not.equal('foo');
diff --git a/src/ui/public/chrome/__tests__/TabCollection.js b/src/ui/public/chrome/__tests__/TabCollection.js
index fa12a4454fab8..631c1e5ba553f 100644
--- a/src/ui/public/chrome/__tests__/TabCollection.js
+++ b/src/ui/public/chrome/__tests__/TabCollection.js
@@ -1,7 +1,7 @@
 const expect = require('expect.js');
 const { indexBy, random } = require('lodash');
 
-const TabFakeStore = require('./_TabFakeStore');
+const StubBrowserStorage = require('testUtils/stub_browser_storage');
 const TabCollection = require('../TabCollection');
 const Tab = require('../Tab');
 
@@ -54,7 +54,7 @@ describe('Chrome TabCollection', function () {
 
   describe('#consumeRouteUpdate()', function () {
     it('updates the active tab', function () {
-      const store = new TabFakeStore();
+      const store = new StubBrowserStorage();
       const baseUrl = `http://localhost:${random(1000, 9999)}`;
       const tabs = new TabCollection({ store, defaults: { baseUrl } });
       tabs.set([
diff --git a/src/ui/public/chrome/__tests__/_TabFakeStore.js b/src/ui/public/chrome/__tests__/_TabFakeStore.js
deleted file mode 100644
index 1b8ab81602259..0000000000000
--- a/src/ui/public/chrome/__tests__/_TabFakeStore.js
+++ /dev/null
@@ -1,9 +0,0 @@
-const store = Symbol('store');
-
-export default class TabFakeStore {
-  constructor() { this[store] = new Map(); }
-  getItem(k) { return this[store].get(k); }
-  setItem(k, v) { return this[store].set(k, v); }
-  getKeys() { return [ ...this[store].keys() ]; }
-  getValues() { return [ ...this[store].values() ]; }
-}
diff --git a/src/ui/public/chrome/api/__tests__/apps.js b/src/ui/public/chrome/api/__tests__/apps.js
index ddb53ada7186e..4e4d8c9857bd6 100644
--- a/src/ui/public/chrome/api/__tests__/apps.js
+++ b/src/ui/public/chrome/api/__tests__/apps.js
@@ -1,7 +1,7 @@
 const expect = require('expect.js');
 
 const setup = require('../apps');
-const TabFakeStore = require('../../__tests__/_TabFakeStore');
+const StubBrowserStorage = require('testUtils/stub_browser_storage');
 
 describe('Chrome API :: apps', function () {
   describe('#get/setShowAppsLink()', function () {
@@ -147,13 +147,13 @@ describe('Chrome API :: apps', function () {
     describe('#get/setLastUrlFor()', function () {
       it('reads/writes last url from storage', function () {
         const chrome = {};
-        const store = new TabFakeStore();
+        const store = new StubBrowserStorage();
         setup(chrome, { appUrlStore: store });
-        expect(chrome.getLastUrlFor('app')).to.equal(undefined);
+        expect(chrome.getLastUrlFor('app')).to.equal(null);
         chrome.setLastUrlFor('app', 'url');
         expect(chrome.getLastUrlFor('app')).to.equal('url');
-        expect(store.getKeys().length).to.equal(1);
-        expect(store.getValues().shift()).to.equal('url');
+        expect(store._getKeys().length).to.equal(1);
+        expect(store._getValues().shift()).to.equal('url');
       });
     });
   });