diff --git a/manifest.json b/manifest.json
index 4c43b64..39d14f4 100644
--- a/manifest.json
+++ b/manifest.json
@@ -40,5 +40,11 @@
   ],
   "options_ui": {
     "page": "build/settings.html"
+  },
+  "browser_action": {
+    "default_icon": {
+      "32": "resources/enabled_32x32.png"
+    },
+    "default_title": "Vim Vixen"
   }
 }
diff --git a/resources/disabled_32x32.png b/resources/disabled_32x32.png
new file mode 100644
index 0000000..d3b88db
Binary files /dev/null and b/resources/disabled_32x32.png differ
diff --git a/resources/enabled_32x32.png b/resources/enabled_32x32.png
new file mode 100644
index 0000000..eaf2862
Binary files /dev/null and b/resources/enabled_32x32.png differ
diff --git a/src/background/actions/command.js b/src/background/actions/command.js
index 4c52bca..2f7305a 100644
--- a/src/background/actions/command.js
+++ b/src/background/actions/command.js
@@ -1,5 +1,5 @@
 import actions from '../actions';
-import * as tabs from 'background/tabs';
+import * as tabs from '../shared/tabs';
 import * as parsers from 'shared/commands/parsers';
 import * as properties from 'shared/settings/properties';
 
diff --git a/src/background/actions/index.js b/src/background/actions/index.js
index 2bdaaf2..3833389 100644
--- a/src/background/actions/index.js
+++ b/src/background/actions/index.js
@@ -5,4 +5,7 @@ export default {
 
   // Find
   FIND_SET_KEYWORD: 'find.set.keyword',
+
+  // Tab
+  TAB_SELECTED: 'tab.selected',
 };
diff --git a/src/background/actions/operation.js b/src/background/actions/operation.js
deleted file mode 100644
index 10c366f..0000000
--- a/src/background/actions/operation.js
+++ /dev/null
@@ -1,92 +0,0 @@
-import operations from 'shared/operations';
-import messages from 'shared/messages';
-import * as tabs from 'background/tabs';
-import * as zooms from 'background/zooms';
-
-const sendConsoleShowCommand = (tab, command) => {
-  return browser.tabs.sendMessage(tab.id, {
-    type: messages.CONSOLE_SHOW_COMMAND,
-    command,
-  });
-};
-
-// This switch statement is only gonna get longer as more
-// features are added, so disable complexity check
-/* eslint-disable complexity */
-const exec = (operation, tab) => {
-  switch (operation.type) {
-  case operations.TAB_CLOSE:
-    return tabs.closeTab(tab.id);
-  case operations.TAB_CLOSE_FORCE:
-    return tabs.closeTabForce(tab.id);
-  case operations.TAB_REOPEN:
-    return tabs.reopenTab();
-  case operations.TAB_PREV:
-    return tabs.selectPrevTab(tab.index, operation.count);
-  case operations.TAB_NEXT:
-    return tabs.selectNextTab(tab.index, operation.count);
-  case operations.TAB_FIRST:
-    return tabs.selectFirstTab();
-  case operations.TAB_LAST:
-    return tabs.selectLastTab();
-  case operations.TAB_PREV_SEL:
-    return tabs.selectPrevSelTab();
-  case operations.TAB_RELOAD:
-    return tabs.reload(tab, operation.cache);
-  case operations.TAB_PIN:
-    return tabs.updateTabPinned(tab, true);
-  case operations.TAB_UNPIN:
-    return tabs.updateTabPinned(tab, false);
-  case operations.TAB_TOGGLE_PINNED:
-    return tabs.toggleTabPinned(tab);
-  case operations.TAB_DUPLICATE:
-    return tabs.duplicate(tab.id);
-  case operations.ZOOM_IN:
-    return zooms.zoomIn();
-  case operations.ZOOM_OUT:
-    return zooms.zoomOut();
-  case operations.ZOOM_NEUTRAL:
-    return zooms.neutral();
-  case operations.COMMAND_SHOW:
-    return sendConsoleShowCommand(tab, '');
-  case operations.COMMAND_SHOW_OPEN:
-    if (operation.alter) {
-      // alter url
-      return sendConsoleShowCommand(tab, 'open ' + tab.url);
-    }
-    return sendConsoleShowCommand(tab, 'open ');
-  case operations.COMMAND_SHOW_TABOPEN:
-    if (operation.alter) {
-      // alter url
-      return sendConsoleShowCommand(tab, 'tabopen ' + tab.url);
-    }
-    return sendConsoleShowCommand(tab, 'tabopen ');
-  case operations.COMMAND_SHOW_WINOPEN:
-    if (operation.alter) {
-      // alter url
-      return sendConsoleShowCommand(tab, 'winopen ' + tab.url);
-    }
-    return sendConsoleShowCommand(tab, 'winopen ');
-  case operations.COMMAND_SHOW_BUFFER:
-    return sendConsoleShowCommand(tab, 'buffer ');
-  case operations.FIND_START:
-    return browser.tabs.sendMessage(tab.id, {
-      type: messages.CONSOLE_SHOW_FIND
-    });
-  case operations.CANCEL:
-    return browser.tabs.sendMessage(tab.id, {
-      type: messages.CONSOLE_HIDE,
-    });
-  case operations.PAGE_SOURCE:
-    return browser.tabs.create({
-      url: 'view-source:' + tab.url,
-      index: tab.index + 1,
-      openerTabId: tab.id,
-    });
-  default:
-    return Promise.resolve();
-  }
-};
-/* eslint-enable complexity */
-
-export { exec };
diff --git a/src/background/actions/tab.js b/src/background/actions/tab.js
index 3c642fd..0d439fd 100644
--- a/src/background/actions/tab.js
+++ b/src/background/actions/tab.js
@@ -1,3 +1,5 @@
+import actions from './index';
+
 const openNewTab = (url, openerTabId, background = false, adjacent = false) => {
   if (adjacent) {
     return browser.tabs.query({
@@ -18,4 +20,11 @@ const openToTab = (url, tab) => {
   return browser.tabs.update(tab.id, { url: url });
 };
 
-export { openNewTab, openToTab };
+const selected = (tabId) => {
+  return {
+    type: actions.TAB_SELECTED,
+    tabId,
+  };
+};
+
+export { openNewTab, openToTab, selected };
diff --git a/src/background/components/background.js b/src/background/components/background.js
index fae3fbb..e13424b 100644
--- a/src/background/components/background.js
+++ b/src/background/components/background.js
@@ -1,10 +1,9 @@
 import messages from 'shared/messages';
-import * as operationActions from 'background/actions/operation';
 import * as commandActions from 'background/actions/command';
 import * as settingActions from 'background/actions/setting';
 import * as findActions from 'background/actions/find';
 import * as tabActions from 'background/actions/tab';
-import * as commands from 'shared/commands';
+import * as completions from '../shared/completions';
 
 export default class BackgroundComponent {
   constructor(store) {
@@ -27,10 +26,6 @@ export default class BackgroundComponent {
     let find = this.store.getState().find;
 
     switch (message.type) {
-    case messages.BACKGROUND_OPERATION:
-      return this.store.dispatch(
-        operationActions.exec(message.operation, sender.tab),
-        sender);
     case messages.OPEN_URL:
       if (message.newTab) {
         let action = tabActions.openNewTab(
@@ -49,7 +44,7 @@ export default class BackgroundComponent {
     case messages.SETTINGS_QUERY:
       return Promise.resolve(this.store.getState().setting.value);
     case messages.CONSOLE_QUERY_COMPLETIONS:
-      return commands.complete(message.text, settings.value);
+      return completions.complete(message.text, settings.value);
     case messages.SETTINGS_RELOAD:
       this.store.dispatch(settingActions.load());
       return this.broadcastSettingsChanged();
diff --git a/src/background/components/indicator.js b/src/background/components/indicator.js
new file mode 100644
index 0000000..cceb119
--- /dev/null
+++ b/src/background/components/indicator.js
@@ -0,0 +1,45 @@
+import * as indicators from '../shared/indicators';
+import messages from 'shared/messages';
+
+export default class IndicatorComponent {
+  constructor(store) {
+    this.store = store;
+
+    messages.onMessage(this.onMessage.bind(this));
+
+    browser.browserAction.onClicked.addListener(this.onClicked);
+    browser.tabs.onActivated.addListener((info) => {
+      return browser.tabs.query({ currentWindow: true }).then(() => {
+        return this.onTabActivated(info);
+      });
+    });
+  }
+
+  onTabActivated(info) {
+    return browser.tabs.sendMessage(info.tabId, {
+      type: messages.ADDON_ENABLED_QUERY,
+    }).then((resp) => {
+      return this.updateIndicator(resp.enabled);
+    });
+  }
+
+  onClicked(tab) {
+    browser.tabs.sendMessage(tab.id, {
+      type: messages.ADDON_TOGGLE_ENABLED,
+    });
+  }
+
+  onMessage(message) {
+    switch (message.type) {
+    case messages.ADDON_ENABLED_RESPONSE:
+      return this.updateIndicator(message.enabled);
+    }
+  }
+
+  updateIndicator(enabled) {
+    if (enabled) {
+      return indicators.enable();
+    }
+    return indicators.disable();
+  }
+}
diff --git a/src/background/components/operation.js b/src/background/components/operation.js
new file mode 100644
index 0000000..9a0b4e1
--- /dev/null
+++ b/src/background/components/operation.js
@@ -0,0 +1,118 @@
+import messages from 'shared/messages';
+import operations from 'shared/operations';
+import * as tabs from '../shared//tabs';
+import * as zooms from '../shared/zooms';
+
+export default class BackgroundComponent {
+  constructor(store) {
+    this.store = store;
+
+    browser.runtime.onMessage.addListener((message, sender) => {
+      try {
+        return this.onMessage(message, sender);
+      } catch (e) {
+        return browser.tabs.sendMessage(sender.tab.id, {
+          type: messages.CONSOLE_SHOW_ERROR,
+          text: e.message,
+        });
+      }
+    });
+  }
+
+  onMessage(message, sender) {
+    switch (message.type) {
+    case messages.BACKGROUND_OPERATION:
+      return this.store.dispatch(
+        this.exec(message.operation, sender.tab),
+        sender);
+    }
+  }
+
+  // eslint-disable-next-line complexity
+  exec(operation, tab) {
+    let tabState = this.store.getState().tab;
+
+    switch (operation.type) {
+    case operations.TAB_CLOSE:
+      return tabs.closeTab(tab.id);
+    case operations.TAB_CLOSE_FORCE:
+      return tabs.closeTabForce(tab.id);
+    case operations.TAB_REOPEN:
+      return tabs.reopenTab();
+    case operations.TAB_PREV:
+      return tabs.selectPrevTab(tab.index, operation.count);
+    case operations.TAB_NEXT:
+      return tabs.selectNextTab(tab.index, operation.count);
+    case operations.TAB_FIRST:
+      return tabs.selectFirstTab();
+    case operations.TAB_LAST:
+      return tabs.selectLastTab();
+    case operations.TAB_PREV_SEL:
+      if (tabState.previousSelected > 0) {
+        return tabs.selectTab(tabState.previousSelected);
+      }
+      break;
+    case operations.TAB_RELOAD:
+      return tabs.reload(tab, operation.cache);
+    case operations.TAB_PIN:
+      return tabs.updateTabPinned(tab, true);
+    case operations.TAB_UNPIN:
+      return tabs.updateTabPinned(tab, false);
+    case operations.TAB_TOGGLE_PINNED:
+      return tabs.toggleTabPinned(tab);
+    case operations.TAB_DUPLICATE:
+      return tabs.duplicate(tab.id);
+    case operations.ZOOM_IN:
+      return zooms.zoomIn();
+    case operations.ZOOM_OUT:
+      return zooms.zoomOut();
+    case operations.ZOOM_NEUTRAL:
+      return zooms.neutral();
+    case operations.COMMAND_SHOW:
+      return this.sendConsoleShowCommand(tab, '');
+    case operations.COMMAND_SHOW_OPEN:
+      if (operation.alter) {
+        // alter url
+        return this.sendConsoleShowCommand(tab, 'open ' + tab.url);
+      }
+      return this.sendConsoleShowCommand(tab, 'open ');
+    case operations.COMMAND_SHOW_TABOPEN:
+      if (operation.alter) {
+        // alter url
+        return this.sendConsoleShowCommand(tab, 'tabopen ' + tab.url);
+      }
+      return this.sendConsoleShowCommand(tab, 'tabopen ');
+    case operations.COMMAND_SHOW_WINOPEN:
+      if (operation.alter) {
+        // alter url
+        return this.sendConsoleShowCommand(tab, 'winopen ' + tab.url);
+      }
+      return this.sendConsoleShowCommand(tab, 'winopen ');
+    case operations.COMMAND_SHOW_BUFFER:
+      return this.sendConsoleShowCommand(tab, 'buffer ');
+    case operations.FIND_START:
+      return browser.tabs.sendMessage(tab.id, {
+        type: messages.CONSOLE_SHOW_FIND
+      });
+    case operations.CANCEL:
+      return browser.tabs.sendMessage(tab.id, {
+        type: messages.CONSOLE_HIDE,
+      });
+    case operations.PAGE_SOURCE:
+      return browser.tabs.create({
+        url: 'view-source:' + tab.url,
+        index: tab.index + 1,
+        openerTabId: tab.id,
+      });
+    default:
+      return Promise.resolve();
+    }
+  }
+
+  sendConsoleShowCommand(tab, command) {
+    return browser.tabs.sendMessage(tab.id, {
+      type: messages.CONSOLE_SHOW_COMMAND,
+      command,
+    });
+  }
+}
diff --git a/src/background/components/tab.js b/src/background/components/tab.js
new file mode 100644
index 0000000..b273546
--- /dev/null
+++ b/src/background/components/tab.js
@@ -0,0 +1,17 @@
+import * as tabActions from '../actions/tab';
+
+export default class TabComponent {
+  constructor(store) {
+    this.store = store;
+
+    browser.tabs.onActivated.addListener((info) => {
+      return browser.tabs.query({ currentWindow: true }).then(() => {
+        return this.onTabActivated(info);
+      });
+    });
+  }
+
+  onTabActivated(info) {
+    return this.store.dispatch(tabActions.selected(info.tabId));
+  }
+}
diff --git a/src/background/index.js b/src/background/index.js
index ff27796..3f1013c 100644
--- a/src/background/index.js
+++ b/src/background/index.js
@@ -1,6 +1,9 @@
 import * as settingActions from 'background/actions/setting';
 import messages from 'shared/messages';
 import BackgroundComponent from 'background/components/background';
+import OperationComponent from 'background/components/operation';
+import TabComponent from 'background/components/tab';
+import IndicatorComponent from 'background/components/indicator';
 import reducers from 'background/reducers';
 import { createStore } from 'shared/store';
 import * as versions from 'shared/versions';
@@ -14,8 +17,13 @@ const store = createStore(reducers, (e, sender) => {
     });
   }
 });
-// eslint-disable-next-line no-unused-vars
+
+/* eslint-disable no-unused-vars */
 const backgroundComponent = new BackgroundComponent(store);
+const operationComponent = new OperationComponent(store);
+const tabComponent = new TabComponent(store);
+const indicatorComponent = new IndicatorComponent(store);
+/* eslint-enable no-unused-vars */
 
 store.dispatch(settingActions.load());
 
diff --git a/src/background/reducers/index.js b/src/background/reducers/index.js
index 63ff0f8..5729f0a 100644
--- a/src/background/reducers/index.js
+++ b/src/background/reducers/index.js
@@ -1,15 +1,18 @@
 import settingReducer from './setting';
 import findReducer from './find';
+import tabReducer from './tab';
 
 // Make setting reducer instead of re-use
 const defaultState = {
   setting: settingReducer(undefined, {}),
   find: findReducer(undefined, {}),
+  tab: tabReducer(undefined, {}),
 };
 
 export default function reducer(state = defaultState, action = {}) {
   return Object.assign({}, state, {
     setting: settingReducer(state.setting, action),
     find: findReducer(state.find, action),
+    tab: tabReducer(state.tab, action),
   });
 }
diff --git a/src/background/reducers/tab.js b/src/background/reducers/tab.js
new file mode 100644
index 0000000..e0cdf32
--- /dev/null
+++ b/src/background/reducers/tab.js
@@ -0,0 +1,19 @@
+import actions from 'background/actions';
+
+const defaultState = {
+  previousSelected: -1,
+  currentSelected: -1,
+};
+
+export default function reducer(state = defaultState, action = {}) {
+  switch (action.type) {
+  case actions.TAB_SELECTED:
+    return {
+      previousSelected: state.currentSelected,
+      currentSelected: action.tabId,
+    };
+  default:
+    return state;
+  }
+}
+
diff --git a/src/background/histories.js b/src/background/shared/completions/histories.js
similarity index 100%
rename from src/background/histories.js
rename to src/background/shared/completions/histories.js
diff --git a/src/shared/commands/complete.js b/src/background/shared/completions/index.js
similarity index 94%
rename from src/shared/commands/complete.js
rename to src/background/shared/completions/index.js
index 0bdbab8..73b7b27 100644
--- a/src/shared/commands/complete.js
+++ b/src/background/shared/completions/index.js
@@ -1,5 +1,5 @@
-import * as tabs from 'background/tabs';
-import * as histories from 'background/histories';
+import * as tabs from './tabs';
+import * as histories from './histories';
 
 const getOpenCompletions = (command, keywords, searchConfig) => {
   return histories.getCompletions(keywords).then((pages) => {
@@ -81,4 +81,4 @@ const complete = (line, settings) => {
   return getCompletions(line, settings);
 };
 
-export default complete;
+export { complete };
diff --git a/src/background/shared/completions/tabs.js b/src/background/shared/completions/tabs.js
new file mode 100644
index 0000000..5edddca
--- /dev/null
+++ b/src/background/shared/completions/tabs.js
@@ -0,0 +1,10 @@
+const getCompletions = (keyword) => {
+  return browser.tabs.query({ currentWindow: true }).then((tabs) => {
+    let matched = tabs.filter((t) => {
+      return t.url.includes(keyword) || t.title && t.title.includes(keyword);
+    });
+    return matched;
+  });
+};
+
+export { getCompletions };
diff --git a/src/background/shared/indicators.js b/src/background/shared/indicators.js
new file mode 100644
index 0000000..74002c4
--- /dev/null
+++ b/src/background/shared/indicators.js
@@ -0,0 +1,13 @@
+const enable = () => {
+  return browser.browserAction.setIcon({
+    path: 'resources/enabled_32x32.png',
+  });
+};
+
+const disable = () => {
+  return browser.browserAction.setIcon({
+    path: 'resources/disabled_32x32.png',
+  });
+};
+
+export { enable, disable };
diff --git a/src/background/tabs.js b/src/background/shared/tabs.js
similarity index 81%
rename from src/background/tabs.js
rename to src/background/shared/tabs.js
index e939870..f1dcc73 100644
--- a/src/background/tabs.js
+++ b/src/background/shared/tabs.js
@@ -1,13 +1,3 @@
-let prevSelTab = 1;
-let currSelTab = 1;
-
-browser.tabs.onActivated.addListener((activeInfo) => {
-  return browser.tabs.query({ currentWindow: true }).then(() => {
-    prevSelTab = currSelTab;
-    currSelTab = activeInfo.tabId;
-  });
-});
-
 const closeTab = (id) => {
   return browser.tabs.get(id).then((tab) => {
     if (!tab.pinned) {
@@ -66,15 +56,6 @@ const selectByKeyword = (current, keyword) => {
   });
 };
 
-const getCompletions = (keyword) => {
-  return browser.tabs.query({ currentWindow: true }).then((tabs) => {
-    let matched = tabs.filter((t) => {
-      return t.url.includes(keyword) || t.title && t.title.includes(keyword);
-    });
-    return matched;
-  });
-};
-
 const selectPrevTab = (current, count) => {
   return browser.tabs.query({ currentWindow: true }).then((tabs) => {
     if (tabs.length < 2) {
@@ -111,8 +92,8 @@ const selectLastTab = () => {
   });
 };
 
-const selectPrevSelTab = () => {
-  return browser.tabs.update(prevSelTab, { active: true });
+const selectTab = (id) => {
+  return browser.tabs.update(id, { active: true });
 };
 
 const reload = (current, cache) => {
@@ -139,7 +120,7 @@ const duplicate = (id) => {
 
 export {
   closeTab, closeTabForce, reopenTab, selectAt, selectByKeyword,
-  getCompletions, selectPrevTab, selectNextTab, selectFirstTab,
-  selectLastTab, selectPrevSelTab, reload, updateTabPinned,
+  selectPrevTab, selectNextTab, selectFirstTab,
+  selectLastTab, selectTab, reload, updateTabPinned,
   toggleTabPinned, duplicate
 };
diff --git a/src/background/zooms.js b/src/background/shared/zooms.js
similarity index 100%
rename from src/background/zooms.js
rename to src/background/shared/zooms.js
diff --git a/src/content/components/common/index.js b/src/content/components/common/index.js
index 565632c..9b7b083 100644
--- a/src/content/components/common/index.js
+++ b/src/content/components/common/index.js
@@ -3,6 +3,7 @@ import KeymapperComponent from './keymapper';
 import FollowComponent from './follow';
 import * as settingActions from 'content/actions/setting';
 import messages from 'shared/messages';
+import * as addonActions from '../../actions/addon';
 
 export default class Common {
   constructor(win, store) {
@@ -14,16 +15,32 @@ export default class Common {
     input.onKey(key => keymapper.key(key));
 
     this.store = store;
+    this.prevEnabled = undefined;
 
     this.reloadSettings();
 
     messages.onMessage(this.onMessage.bind(this));
+    store.subscribe(() => this.update());
   }
 
   onMessage(message) {
     switch (message.type) {
     case messages.SETTINGS_CHANGED:
-      this.reloadSettings();
+      return this.reloadSettings();
+    case messages.ADDON_TOGGLE_ENABLED:
+      return this.store.dispatch(addonActions.toggleEnabled());
+    }
+  }
+
+  update() {
+    let enabled = this.store.getState().addon.enabled;
+    if (enabled !== this.prevEnabled) {
+      this.prevEnabled = enabled;
+
+      browser.runtime.sendMessage({
+        type: messages.ADDON_ENABLED_RESPONSE,
+        enabled,
+      });
     }
   }
 
diff --git a/src/content/components/top-content/index.js b/src/content/components/top-content/index.js
index cf21ec4..a0d0480 100644
--- a/src/content/components/top-content/index.js
+++ b/src/content/components/top-content/index.js
@@ -44,15 +44,24 @@ export default class TopContent {
       .some(regex => regex.test(partial));
     if (matched) {
       this.store.dispatch(addonActions.disable());
+    } else {
+      this.store.dispatch(addonActions.enable());
     }
   }
 
   onMessage(message) {
+    let addonState = this.store.getState().addon;
+
     switch (message.type) {
     case messages.CONSOLE_UNFOCUS:
       this.win.focus();
       consoleFrames.blur(window.document);
       return Promise.resolve();
+    case messages.ADDON_ENABLED_QUERY:
+      return Promise.resolve({
+        type: messages.ADDON_ENABLED_RESPONSE,
+        enabled: addonState.enabled,
+      });
     }
   }
 }
diff --git a/src/shared/commands/index.js b/src/shared/commands/index.js
deleted file mode 100644
index 78cb4df..0000000
--- a/src/shared/commands/index.js
+++ /dev/null
@@ -1,3 +0,0 @@
-import complete from './complete';
-
-export { complete };
diff --git a/src/shared/messages.js b/src/shared/messages.js
index a404658..1f9c816 100644
--- a/src/shared/messages.js
+++ b/src/shared/messages.js
@@ -48,6 +48,10 @@ export default {
   FIND_GET_KEYWORD: 'find.get.keyword',
   FIND_SET_KEYWORD: 'find.set.keyword',
 
+  ADDON_ENABLED_QUERY: 'addon.enabled.query',
+  ADDON_ENABLED_RESPONSE: 'addon.enabled.response',
+  ADDON_TOGGLE_ENABLED: 'addon.toggle.enabled',
+
   OPEN_URL: 'open.url',
 
   SETTINGS_RELOAD: 'settings.reload',
diff --git a/test/background/actions/tab.test.js b/test/background/actions/tab.test.js
new file mode 100644
index 0000000..ab57374
--- /dev/null
+++ b/test/background/actions/tab.test.js
@@ -0,0 +1,13 @@
+import actions from 'background/actions';
+import * as tabActions from 'background/actions/tab';
+
+describe("tab actions", () => {
+  describe("selected", () => {
+    it('create TAB_SELECTED action', () => {
+      let action = tabActions.selected(123);
+      expect(action.type).to.equal(actions.TAB_SELECTED);
+      expect(action.tabId).to.equal(123);
+    });
+  });
+});
+
diff --git a/test/background/reducers/tab.test.js b/test/background/reducers/tab.test.js
new file mode 100644
index 0000000..09fa8a7
--- /dev/null
+++ b/test/background/reducers/tab.test.js
@@ -0,0 +1,22 @@
+import actions from 'background/actions';
+import tabReducer from 'background/reducers/tab';
+
+describe("tab reducer", () => {
+  it('return the initial state', () => {
+    let state = tabReducer(undefined, {});
+    expect(state.previousSelected).to.equal(-1);
+    expect(state.currentSelected).to.equal(-1);
+  });
+
+  it('return next state for TAB_SELECTED', () => {
+    let state = undefined;
+
+    state = tabReducer(state, { type: actions.TAB_SELECTED, tabId: 123 });
+    expect(state.previousSelected).to.equal(-1);
+    expect(state.currentSelected).to.equal(123);
+
+    state = tabReducer(state, { type: actions.TAB_SELECTED, tabId: 456 });
+    expect(state.previousSelected).to.equal(123);
+    expect(state.currentSelected).to.equal(456);
+  });
+});