diff --git a/packages/core/__tests__/tags.test.js b/packages/core/__tests__/tags.test.js
index 9d9988875..815ed721c 100644
--- a/packages/core/__tests__/tags.test.js
+++ b/packages/core/__tests__/tags.test.js
@@ -78,4 +78,14 @@ describe.each([
       tag = db[collection].tag(tag.id);
       expect(tag.alias).toBe(value + "-new");
     }));
+
+  test(`remove a ${action}`, () =>
+    noteTest().then(async ({ db, id }) => {
+      let note = db.notes.note(id);
+      await note[action](value);
+
+      let tag = db[collection].tag(value);
+      await db[collection].remove(tag.id);
+      expect(db[collection].tag(value)).toBeUndefined();
+    }));
 });
diff --git a/packages/core/collections/notes.js b/packages/core/collections/notes.js
index 20daff80a..89d030fd1 100644
--- a/packages/core/collections/notes.js
+++ b/packages/core/collections/notes.js
@@ -34,7 +34,7 @@ export default class Notes extends Collection {
         }
         if (!!oldNote.tags) {
           for (let tag of oldNote.tags) {
-            await this._db.tags.remove(tag, id);
+            await this._db.tags.untag(tag, id);
           }
         }
       }
@@ -285,7 +285,7 @@ export default class Notes extends Collection {
         }
       }
       for (let tag of item.tags) {
-        await this._db.tags.remove(tag, id);
+        await this._db.tags.untag(tag, id);
       }
       if (item.data.color) {
         await this._db.colors.remove(item.data.color, id);
diff --git a/packages/core/collections/tags.js b/packages/core/collections/tags.js
index 87f967b8a..884ae0a0e 100644
--- a/packages/core/collections/tags.js
+++ b/packages/core/collections/tags.js
@@ -1,7 +1,8 @@
 import Collection from "./collection";
 import { qclone } from "qclone";
 import { makeId } from "../utils/id";
-import { deleteItem } from "../utils/array";
+import { deleteItem, deleteItems } from "../utils/array";
+import setManipulator from "../utils/set";
 
 export default class Tags extends Collection {
   tag(id) {
@@ -9,31 +10,29 @@ export default class Tags extends Collection {
     return tagItem;
   }
 
-  async add(tagId, noteId) {
-    if (tagId.id || tagId.title) {
-      tagId = tagId.id;
-    }
-
-    if (!tagId || !noteId) {
-      console.error("tagId and noteId cannot be falsy.");
+  async add(tagId, ...noteIds) {
+    if (!tagId) {
+      console.error("tagId cannot be undefined.");
       return;
     }
 
-    let tag = this.all.find((t) => t.id === tagId || t.title === tagId) || {
+    if (typeof tagId === "object") {
+      tagId = tagId.id;
+    }
+
+    let tag = this.tag(tagId) || {
       title: tagId,
     };
 
     let id = tag.id || makeId(tag.title);
     let notes = tag.noteIds || [];
 
-    if (notes.find((id) => id === noteId)) return id;
-
     tag = {
       type: "tag",
       alias: tag.title,
       id,
       title: tag.title,
-      noteIds: [...notes, noteId],
+      noteIds: setManipulator.union(notes, noteIds),
     };
 
     await this._collection.addItem(tag);
@@ -41,9 +40,9 @@ export default class Tags extends Collection {
   }
 
   async rename(tagId, newName) {
-    let tag = this.all.find((t) => t.id === tagId);
+    let tag = this.tag(tagId);
     if (!tag) {
-      console.error(`No such tag found. Tag id:`, tagId);
+      console.error(`No tag found. Tag id:`, tagId);
       return;
     }
     tag.alias = newName;
@@ -58,26 +57,29 @@ export default class Tags extends Collection {
     return this._collection.getItems();
   }
 
-  async remove(tagTitle, noteId) {
-    if (!tagTitle || !noteId) {
-      console.error(
-        "tag title and noteId cannot be undefined.",
-        tagTitle,
-        noteId
-      );
-      return;
-    }
-
-    let tag = this.all.find((t) => t.title === tagTitle || t.id === tagTitle);
+  async remove(tagId) {
+    let tag = this.tag(tagId);
     if (!tag) {
-      console.error(`No such tag found. Tag title:`, tagTitle);
+      console.error(`No tag found. Tag id:`, tagId);
+      return;
+    }
+    for (let noteId of tag.noteIds) {
+      const note = this._db.notes.note(noteId);
+      if (!note) continue;
+      await note.untag(tagId);
+    }
+    await this._db.settings.unpin(tagId);
+    await this._collection.deleteItem(tagId);
+  }
+
+  async untag(tagId, ...noteIds) {
+    let tag = this.tag(tagId);
+    if (!tag) {
+      console.error(`No such tag found. Tag title:`, tagId);
       return;
     }
 
-    tag = qclone(tag);
-
-    if (!deleteItem(tag.noteIds, noteId))
-      console.error(`No such note exists in tag.`, tag.id, noteId);
+    deleteItems(tag.noteIds, ...noteIds);
 
     if (tag.noteIds.length > 0) await this._collection.addItem(tag);
     else {
diff --git a/packages/core/common.js b/packages/core/common.js
index 6ffe88418..aa0ddc057 100644
--- a/packages/core/common.js
+++ b/packages/core/common.js
@@ -3,6 +3,8 @@ import EventManager from "./utils/event-manager";
 export const EV = new EventManager();
 
 export async function sendCheckUserStatusEvent(type) {
+  if (process.env.NODE_ENV === "testing") return true;
+
   const results = await EV.publishWithResult(EVENTS.userCheckStatus, type);
   if (typeof results === "boolean") return results;
   return results.some((r) => r.type === type && r.result === true);
diff --git a/packages/core/jest.setup.js b/packages/core/jest.setup.js
index 03b1e48eb..8c8c057d1 100644
--- a/packages/core/jest.setup.js
+++ b/packages/core/jest.setup.js
@@ -1,6 +1,8 @@
 var nodeCrypto = require("crypto");
 var jsdom = require("jsdom");
 
+process.env.NODE_ENV = "testing";
+
 const dom = new jsdom.JSDOM("", {});
 global.window = dom.window;
 global.document = dom.window.document;
diff --git a/packages/core/models/note.js b/packages/core/models/note.js
index 0eb3cc50f..f7ba24c1c 100644
--- a/packages/core/models/note.js
+++ b/packages/core/models/note.js
@@ -101,7 +101,7 @@ export default class Note {
 
   async uncolor() {
     if (!this._note.color) return;
-    await this._db.colors.remove(this._note.color, this._note.id);
+    await this._db.colors.untag(this._note.color, this._note.id);
     await this._db.notes._collection.addItem({
       ...this._note,
       color: undefined,
@@ -136,7 +136,8 @@ export default class Note {
 
 async function addTag(tag) {
   if (this._note.tags.indexOf(tag) > -1)
-    throw new Error("Cannot add a duplicate tag.");
+    return console.error("Cannot add a duplicate tag.");
+
   let tagItem = await this._db.tags.add(tag, this._note.id);
   let arr = [...this._note.tags, tagItem.title];
   const note = { ...this._note, tags: arr };
@@ -145,10 +146,11 @@ async function addTag(tag) {
 
 async function removeTag(tag) {
   if (this._note.tags.indexOf(tag) <= -1)
-    throw new Error("This note is not tagged by the specified tag.");
+    return console.error("This note is not tagged by the specified tag.");
+
   let arr = [...this._note.tags];
   arr.splice(arr.indexOf(tag), 1);
   const note = { ...this._note, tags: arr };
-  await this._db.tags.remove(tag, note.id);
+  await this._db.tags.untag(tag, note.id);
   await this._db.notes._collection.addItem(note);
 }
diff --git a/packages/core/utils/array.js b/packages/core/utils/array.js
index 0ab1a473c..79d8165b5 100644
--- a/packages/core/utils/array.js
+++ b/packages/core/utils/array.js
@@ -6,6 +6,12 @@ export function deleteItem(array, item) {
   return deleteAtIndex(array, array.indexOf(item));
 }
 
+export function deleteItems(array, ...items) {
+  for (let item of items) {
+    deleteItem(array, item);
+  }
+}
+
 export function findById(array, id) {
   return array.find((item) => item.id === id);
 }