From b39996616c33de90bb82e3d7a009c865cf2b0f0c Mon Sep 17 00:00:00 2001
From: Peter Savchenko <specc.dev@gmail.com>
Date: Tue, 8 Aug 2023 22:17:09 +0300
Subject: [PATCH] chore(perf): initialisation and rendering performance
 optimisations (#2430)

* renderer batching

* initialization and rendering performance optimized

* insertMany api method added

* Update index.html

* rm old method

* upd changelog

* upd paragraph

* paste tests fixed

* api blocks tests fixed

* backspace event tests fixed

* async issues in tests fixed

* eslint

* stub block added, tests added

* eslint

* eslint

* add test for insertMany()

* Update package.json
---
 cypress.config.ts                             |  15 +-
 docs/CHANGELOG.md                             |  11 +-
 index.html                                    |   2 +
 package.json                                  |   5 +-
 src/components/block/index.ts                 |  19 +-
 src/components/blocks.ts                      |  38 ++++
 src/components/core.ts                        |  40 ++--
 src/components/modules/api/blocks.ts          |  58 +++++-
 src/components/modules/blockEvents.ts         |  10 +-
 src/components/modules/blockManager.ts        |  94 ++++++---
 src/components/modules/caret.ts               |  17 +-
 src/components/modules/paste.ts               |   9 +-
 src/components/modules/renderer.ts            | 182 ++++++++----------
 src/components/modules/saver.ts               |  22 +--
 src/components/modules/toolbar/index.ts       |  62 ++++--
 src/components/modules/toolbar/inline.ts      |   9 +-
 src/components/modules/ui.ts                  |  35 +---
 src/components/polyfills.ts                   |  24 +++
 src/components/selection.ts                   |   2 +-
 src/components/utils.ts                       |   1 +
 src/components/utils/events.ts                |   8 +-
 src/components/utils/promise-queue.ts         |  28 +++
 src/styles/stub.css                           |  29 ++-
 src/styles/ui.css                             |  50 +----
 src/tools/stub/index.ts                       |   3 +-
 test/cypress/.eslintrc                        |   4 +-
 test/cypress/support/commands.ts              |  13 +-
 test/cypress/support/index.ts                 |   3 +
 test/cypress/tests/api/blocks.cy.ts           | 167 +++++++++-------
 test/cypress/tests/block-ids.cy.ts            |  55 +++---
 test/cypress/tests/copy-paste.cy.ts           | 116 ++++++-----
 test/cypress/tests/i18n.cy.ts                 |   3 +-
 .../tests/modules/BlockEvents/Backspace.cy.ts |   6 +-
 .../tests/modules/BlockEvents/Enter.cy.ts     |   3 -
 test/cypress/tests/modules/Renderer.cy.ts     | 149 ++++++++++++++
 test/cypress/tests/onchange.cy.ts             |  83 +++++++-
 test/cypress/tests/sanitisation.cy.ts         |  62 +++---
 test/cypress/tests/utils/flipper.cy.ts        |  36 ++--
 types/api/blocks.d.ts                         |  11 +-
 vite.config.js                                |   2 +-
 yarn.lock                                     |  36 +++-
 41 files changed, 991 insertions(+), 531 deletions(-)
 create mode 100644 src/components/utils/promise-queue.ts
 create mode 100644 test/cypress/tests/modules/Renderer.cy.ts

diff --git a/cypress.config.ts b/cypress.config.ts
index ed2c10f0..11ac2de2 100644
--- a/cypress.config.ts
+++ b/cypress.config.ts
@@ -11,9 +11,22 @@ export default defineConfig({
     // We've imported your old cypress plugins here.
     // You may want to clean this up later by importing these.
     setupNodeEvents(on, config) {
-      return require('./test/cypress/plugins/index.ts')(on, config);
+      /**
+       * Plugin for cypress that adds better terminal output for easier debugging.
+       * Prints cy commands, browser console logs, cy.request and cy.intercept data. Great for your pipelines.
+       * https://github.com/archfz/cypress-terminal-report
+       */
+      require('cypress-terminal-report/src/installLogsPrinter')(on);
+
+      require('./test/cypress/plugins/index.ts')(on, config);
     },
     specPattern: 'test/cypress/tests/**/*.cy.{js,jsx,ts,tsx}',
     supportFile: 'test/cypress/support/index.ts',
   },
+  'retries': {
+    // Configure retry attempts for `cypress run`
+    'runMode': 2,
+    // Configure retry attempts for `cypress open`
+    'openMode': 0,
+  },
 });
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 6600d997..daaaee87 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -3,12 +3,21 @@
 ### 2.28.0
 
 - `New` - Block ids now displayed in DOM via a data-id attribute. Could be useful for plugins that want access a Block's element by id.
-- `New` - The `.convert(blockId, newType)` API method added
+- `New` - The `blocks.convert(blockId, newType)` API method added. It allows to convert existed Block to a Block of another type.
+- `New` - The `blocks.insertMany()` API method added. It allows to insert several Blocks to specified index.
 - `Improvement` - The Delete keydown at the end of the Block will now work opposite a Backspace at the start. Next Block will be removed (if empty) or merged with the current one.
 - `Improvement` - The Delete keydown will work like a Backspace when several Blocks are selected.
 - `Improvement` - If we have two empty Blocks, and press Backspace at the start of the second one, the previous will be removed instead of current.
 - `Improvement` - Tools shortcuts could be used to convert one Block to another.
 - `Improvement` - Tools shortcuts displayed in the Conversion Toolbar
+- `Improvement` - Initialization Loader has been removed.
+- `Improvement` - Selection style won't override your custom style for `::selection` outside the editor.
+- `Improvement` - Performance optimizations: initialization speed increased, `blocks.render()` API method optimized. Big documents will be displayed faster.
+- `Improvement` - "Editor saving" log removed
+- `Improvement` - "I'm ready" log removed
+- `Improvement` - The stub-block style simplified.
+- `Improvement` - If some Block's tool will throw an error during construction, we will show Stub block instead of skipping it during render
+- `Improvement` - Call of `blocks.clear()` now will trigger onChange will "block-removed" event for all removed blocks.
 
 ### 2.27.2
 
diff --git a/index.html b/index.html
index 43c8b4ae..03037f39 100644
--- a/index.html
+++ b/index.html
@@ -404,6 +404,8 @@
 
       localStorage.setItem('theme', document.body.classList.contains("dark-mode") ? 'dark' : 'default');
     })
+
+    window.editor = editor;
   </script>
 </body>
 </html>
diff --git a/package.json b/package.json
index bbb0329f..d5540e50 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@editorjs/editorjs",
-  "version": "2.28.0-rc.1",
+  "version": "2.28.0-rc.2",
   "description": "Editor.js — Native JS, based on API and Open Source",
   "main": "dist/editorjs.umd.js",
   "module": "dist/editorjs.mjs",
@@ -44,7 +44,7 @@
     "@editorjs/code": "^2.7.0",
     "@editorjs/delimiter": "^1.2.0",
     "@editorjs/header": "^2.7.0",
-    "@editorjs/paragraph": "^2.9.0",
+    "@editorjs/paragraph": "^2.10.0",
     "@editorjs/simple-image": "^1.4.1",
     "@types/node": "^18.15.11",
     "chai-subset": "^1.6.0",
@@ -53,6 +53,7 @@
     "core-js": "3.30.0",
     "cypress": "^12.9.0",
     "cypress-intellij-reporter": "^0.0.7",
+    "cypress-terminal-report": "^5.3.2",
     "eslint": "^8.37.0",
     "eslint-config-codex": "^1.7.1",
     "eslint-plugin-chai-friendly": "^0.7.2",
diff --git a/src/components/block/index.ts b/src/components/block/index.ts
index d568f25d..b47fe781 100644
--- a/src/components/block/index.ts
+++ b/src/components/block/index.ts
@@ -252,15 +252,20 @@ export default class Block extends EventsDispatcher<BlockEvents> {
     this.holder = this.compose();
 
     /**
-     * Start watching block mutations
+     * Bind block events in RIC for optimizing of constructing process time
      */
-    this.watchBlockMutations();
+    window.requestIdleCallback(() => {
+      /**
+       * Start watching block mutations
+       */
+      this.watchBlockMutations();
 
-    /**
-     * Mutation observer doesn't track changes in "<input>" and "<textarea>"
-     * so we need to track focus events to update current input and clear cache.
-     */
-    this.addInputEvents();
+      /**
+       * Mutation observer doesn't track changes in "<input>" and "<textarea>"
+       * so we need to track focus events to update current input and clear cache.
+       */
+      this.addInputEvents();
+    });
   }
 
   /**
diff --git a/src/components/blocks.ts b/src/components/blocks.ts
index b3713ad4..a26afff9 100644
--- a/src/components/blocks.ts
+++ b/src/components/blocks.ts
@@ -220,6 +220,44 @@ export default class Blocks {
     }
   }
 
+  /**
+   * Inserts several blocks at once
+   *
+   * @param blocks - blocks to insert
+   * @param index - index to insert blocks at
+   */
+  public insertMany(blocks: Block[], index: number ): void {
+    const fragment = new DocumentFragment();
+
+    for (const block of blocks) {
+      fragment.appendChild(block.holder);
+    }
+
+    if (this.length > 0) {
+      if (index > 0) {
+        const previousBlockIndex = Math.min(index - 1, this.length - 1);
+        const previousBlock = this.blocks[previousBlockIndex];
+
+        previousBlock.holder.after(fragment);
+      } else if (index === 0) {
+        this.workingArea.prepend(fragment);
+      }
+
+      /**
+       * Insert blocks to the array at the specified index
+       */
+      this.blocks.splice(index, 0, ...blocks);
+    } else {
+      this.blocks.push(...blocks);
+      this.workingArea.appendChild(fragment);
+    }
+
+    /**
+     * Call Rendered event for each block
+     */
+    blocks.forEach((block) => block.call(BlockToolAPI.RENDERED));
+  }
+
   /**
    * Remove block
    *
diff --git a/src/components/core.ts b/src/components/core.ts
index acdc93e7..18fe3ff5 100644
--- a/src/components/core.ts
+++ b/src/components/core.ts
@@ -39,7 +39,8 @@ export default class Core {
     /**
      * Ready promise. Resolved if Editor.js is ready to work, rejected otherwise
      */
-    let onReady, onFail;
+    let onReady: (value?: void | PromiseLike<void>) => void;
+    let onFail: (reason?: unknown) => void;
 
     this.isReady = new Promise((resolve, reject) => {
       onReady = resolve;
@@ -50,33 +51,22 @@ export default class Core {
       .then(async () => {
         this.configuration = config;
 
-        await this.validate();
-        await this.init();
+        this.validate();
+        this.init();
         await this.start();
+        await this.render();
 
-        _.logLabeled('I\'m ready! (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧', 'log', '', 'color: #E24A75');
+        const { BlockManager, Caret, UI, ModificationsObserver } = this.moduleInstances;
 
-        setTimeout(async () => {
-          await this.render();
+        UI.checkEmptiness();
+        ModificationsObserver.enable();
 
-          if ((this.configuration as EditorConfig).autofocus) {
-            const { BlockManager, Caret } = this.moduleInstances;
+        if ((this.configuration as EditorConfig).autofocus) {
+          Caret.setToBlock(BlockManager.blocks[0], Caret.positions.START);
+          BlockManager.highlightCurrentNode();
+        }
 
-            Caret.setToBlock(BlockManager.blocks[0], Caret.positions.START);
-            BlockManager.highlightCurrentNode();
-          }
-
-          /**
-           * Remove loader, show content
-           */
-          this.moduleInstances.UI.removeLoader();
-
-          /**
-           * Resolve this.isReady promise
-           */
-          onReady();
-        // eslint-disable-next-line @typescript-eslint/no-magic-numbers
-        }, 500);
+        onReady();
       })
       .catch((error) => {
         _.log(`Editor.js is not ready because of ${error}`, 'error');
@@ -210,10 +200,8 @@ export default class Core {
 
   /**
    * Checks for required fields in Editor's config
-   *
-   * @returns {Promise<void>}
    */
-  public async validate(): Promise<void> {
+  public validate(): void {
     const { holderId, holder } = this.config;
 
     if (holderId && holder) {
diff --git a/src/components/modules/api/blocks.ts b/src/components/modules/api/blocks.ts
index 81cf7a52..b0e92642 100644
--- a/src/components/modules/api/blocks.ts
+++ b/src/components/modules/api/blocks.ts
@@ -1,5 +1,5 @@
 import { BlockAPI as BlockAPIInterface, Blocks } from '../../../../types/api';
-import { BlockToolData, OutputData, ToolConfig } from '../../../../types';
+import { BlockToolData, OutputBlockData, OutputData, ToolConfig } from '../../../../types';
 import * as _ from './../../utils';
 import BlockAPI from '../../block/api';
 import Module from '../../__module';
@@ -32,6 +32,7 @@ export default class BlocksAPI extends Module {
       stretchBlock: (index: number, status = true): void => this.stretchBlock(index, status),
       insertNewBlock: (): void => this.insertNewBlock(),
       insert: this.insert,
+      insertMany: this.insertMany,
       update: this.update,
       composeBlockData: this.composeBlockData,
       convert: this.convert,
@@ -181,8 +182,12 @@ export default class BlocksAPI extends Module {
    *
    * @param {OutputData} data — Saved Editor data
    */
-  public render(data: OutputData): Promise<void> {
-    this.Editor.BlockManager.clear();
+  public async render(data: OutputData): Promise<void> {
+    if (data === undefined || data.blocks === undefined) {
+      throw new Error('Incorrect data passed to the render() method');
+    }
+
+    await this.Editor.BlockManager.clear();
 
     return this.Editor.Renderer.render(data.blocks);
   }
@@ -351,4 +356,51 @@ export default class BlocksAPI extends Module {
       throw new Error(`Conversion from "${blockToConvert.name}" to "${newType}" is not possible. ${unsupportedBlockTypes} tool(s) should provide a "conversionConfig"`);
     }
   };
+
+
+  /**
+   * Inserts several Blocks to a specified index
+   *
+   * @param blocks - blocks data to insert
+   * @param index - index to insert the blocks at
+   */
+  private insertMany = (
+    blocks: OutputBlockData[],
+    index: number = this.Editor.BlockManager.blocks.length - 1
+  ): BlockAPIInterface[] => {
+    this.validateIndex(index);
+
+    const blocksToInsert = blocks.map(({ id, type, data }) => {
+      return this.Editor.BlockManager.composeBlock({
+        id,
+        tool: type || (this.config.defaultBlock as string),
+        data,
+      });
+    });
+
+    this.Editor.BlockManager.insertMany(blocksToInsert, index);
+
+    // we cast to any because our BlockAPI has no "new" signature
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    return blocksToInsert.map((block) => new (BlockAPI as any)(block));
+  };
+
+  /**
+   * Validated block index and throws an error if it's invalid
+   *
+   * @param index - index to validate
+   */
+  private validateIndex(index: unknown): void {
+    if (typeof index !== 'number') {
+      throw new Error('Index should be a number');
+    }
+
+    if (index < 0) {
+      throw new Error(`Index should be greater than or equal to 0`);
+    }
+
+    if (index === null) {
+      throw new Error(`Index should be greater than or equal to 0`);
+    }
+  }
 }
diff --git a/src/components/modules/blockEvents.ts b/src/components/modules/blockEvents.ts
index d60e5bd8..ee2d00c3 100644
--- a/src/components/modules/blockEvents.ts
+++ b/src/components/modules/blockEvents.ts
@@ -454,10 +454,12 @@ export default class BlockEvents extends Module {
     BlockManager
       .mergeBlocks(targetBlock, blockToMerge)
       .then(() => {
-        /** Restore caret position after merge */
-        Caret.restoreCaret(targetBlock.pluginsContent as HTMLElement);
-        targetBlock.pluginsContent.normalize();
-        Toolbar.close();
+        window.requestAnimationFrame(() => {
+          /** Restore caret position after merge */
+          Caret.restoreCaret(targetBlock.pluginsContent as HTMLElement);
+          targetBlock.pluginsContent.normalize();
+          Toolbar.close();
+        });
       });
   }
 
diff --git a/src/components/modules/blockManager.ts b/src/components/modules/blockManager.ts
index 67cae21e..bece7e00 100644
--- a/src/components/modules/blockManager.ts
+++ b/src/components/modules/blockManager.ts
@@ -20,6 +20,7 @@ import { BlockChangedMutationType } from '../../../types/events/block/BlockChang
 import { BlockChanged } from '../events';
 import { clean } from '../utils/sanitizer';
 import { convertStringToBlockData } from '../utils/blocks';
+import PromiseQueue from '../utils/promise-queue';
 
 /**
  * @typedef {BlockManager} BlockManager
@@ -244,7 +245,9 @@ export default class BlockManager extends Module {
     }, this.eventsDispatcher);
 
     if (!readOnly) {
-      this.bindBlockEvents(block);
+      window.requestIdleCallback(() => {
+        this.bindBlockEvents(block);
+      }, { timeout: 2000 });
     }
 
     return block;
@@ -320,6 +323,16 @@ export default class BlockManager extends Module {
     return block;
   }
 
+  /**
+   * Inserts several blocks at once
+   *
+   * @param blocks - blocks to insert
+   * @param index - index where to insert
+   */
+  public insertMany(blocks: Block[], index = 0): void {
+    this._blocks.insertMany(blocks, index);
+  }
+
   /**
    * Replace passed Block with the new one with specified Tool and data
    *
@@ -433,40 +446,48 @@ export default class BlockManager extends Module {
    * Remove passed Block
    *
    * @param block - Block to remove
+   * @param addLastBlock - if true, adds new default block at the end. @todo remove this logic and use event-bus instead
    */
-  public removeBlock(block: Block): void {
-    const index = this._blocks.indexOf(block);
+  public removeBlock(block: Block, addLastBlock = true): Promise<void> {
+    return new Promise((resolve) => {
+      const index = this._blocks.indexOf(block);
 
-    /**
-     * If index is not passed and there is no block selected, show a warning
-     */
-    if (!this.validateIndex(index)) {
-      throw new Error('Can\'t find a Block to remove');
-    }
+      /**
+       * If index is not passed and there is no block selected, show a warning
+       */
+      if (!this.validateIndex(index)) {
+        throw new Error('Can\'t find a Block to remove');
+      }
 
-    block.destroy();
-    this._blocks.remove(index);
+      block.destroy();
+      this._blocks.remove(index);
 
-    /**
-     * Force call of didMutated event on Block removal
-     */
-    this.blockDidMutated(BlockRemovedMutationType, block, {
-      index,
+      /**
+       * Force call of didMutated event on Block removal
+       */
+      this.blockDidMutated(BlockRemovedMutationType, block, {
+        index,
+      });
+
+      if (this.currentBlockIndex >= index) {
+        this.currentBlockIndex--;
+      }
+
+      /**
+       * If first Block was removed, insert new Initial Block and set focus on it`s first input
+       */
+      if (!this.blocks.length) {
+        this.currentBlockIndex = -1;
+
+        if (addLastBlock) {
+          this.insert();
+        }
+      } else if (index === 0) {
+        this.currentBlockIndex = 0;
+      }
+
+      resolve();
     });
-
-    if (this.currentBlockIndex >= index) {
-      this.currentBlockIndex--;
-    }
-
-    /**
-     * If first Block was removed, insert new Initial Block and set focus on it`s first input
-     */
-    if (!this.blocks.length) {
-      this.currentBlockIndex = -1;
-      this.insert();
-    } else if (index === 0) {
-      this.currentBlockIndex = 0;
-    }
   }
 
   /**
@@ -804,8 +825,17 @@ export default class BlockManager extends Module {
    *                                             we don't need to add an empty default block
    *                                        2) in api.blocks.clear we should add empty block
    */
-  public clear(needToAddDefaultBlock = false): void {
-    this._blocks.removeAll();
+  public async clear(needToAddDefaultBlock = false): Promise<void> {
+    const queue = new PromiseQueue();
+
+    this.blocks.forEach((block) => {
+      queue.add(async () => {
+        await this.removeBlock(block, false);
+      });
+    });
+
+    await queue.completed;
+
     this.dropPointer();
 
     if (needToAddDefaultBlock) {
diff --git a/src/components/modules/caret.ts b/src/components/modules/caret.ts
index 0494dcaf..2e870213 100644
--- a/src/components/modules/caret.ts
+++ b/src/components/modules/caret.ts
@@ -503,13 +503,10 @@ export default class Caret extends Module {
 
     sel.expandToTag(shadowCaret as HTMLElement);
 
-    setTimeout(() => {
-      const newRange = document.createRange();
+    const newRange = document.createRange();
 
-      newRange.selectNode(shadowCaret);
-      newRange.extractContents();
-    // eslint-disable-next-line @typescript-eslint/no-magic-numbers
-    }, 50);
+    newRange.selectNode(shadowCaret);
+    newRange.extractContents();
   }
 
   /**
@@ -534,7 +531,7 @@ export default class Caret extends Module {
       fragment.appendChild(new Text());
     }
 
-    const lastChild = fragment.lastChild;
+    const lastChild = fragment.lastChild as ChildNode;
 
     range.deleteContents();
     range.insertNode(fragment);
@@ -542,7 +539,11 @@ export default class Caret extends Module {
     /** Cross-browser caret insertion */
     const newRange = document.createRange();
 
-    newRange.setStart(lastChild, lastChild.textContent.length);
+    const nodeToSetCaret = lastChild.nodeType === Node.TEXT_NODE ? lastChild : lastChild.firstChild;
+
+    if (nodeToSetCaret !== null && nodeToSetCaret.textContent !== null) {
+      newRange.setStart(nodeToSetCaret, nodeToSetCaret.textContent.length);
+    }
 
     selection.removeAllRanges();
     selection.addRange(newRange);
diff --git a/src/components/modules/paste.ts b/src/components/modules/paste.ts
index 299314f5..2324a5d6 100644
--- a/src/components/modules/paste.ts
+++ b/src/components/modules/paste.ts
@@ -479,9 +479,14 @@ export default class Paste extends Module {
   private handlePasteEvent = async (event: ClipboardEvent): Promise<void> => {
     const { BlockManager, Toolbar } = this.Editor;
 
+    /**
+     * When someone pasting into a block, its more stable to set current block by event target, instead of relying on current block set before
+     */
+    const currentBlock = BlockManager.setCurrentBlockByChildNode(event.target as HTMLElement);
+
     /** If target is native input or is not Block, use browser behaviour */
     if (
-      !BlockManager.currentBlock || (this.isNativeBehaviour(event.target) && !event.clipboardData.types.includes('Files'))
+      !currentBlock || (this.isNativeBehaviour(event.target) && !event.clipboardData.types.includes('Files'))
     ) {
       return;
     }
@@ -489,7 +494,7 @@ export default class Paste extends Module {
     /**
      * If Tools is in list of errors, skip processing of paste event
      */
-    if (BlockManager.currentBlock && this.exceptionList.includes(BlockManager.currentBlock.name)) {
+    if (currentBlock && this.exceptionList.includes(currentBlock.name)) {
       return;
     }
 
diff --git a/src/components/modules/renderer.ts b/src/components/modules/renderer.ts
index 988447d7..a3d38e65 100644
--- a/src/components/modules/renderer.ts
+++ b/src/components/modules/renderer.ts
@@ -1,119 +1,107 @@
 import Module from '../__module';
 import * as _ from '../utils';
-import { OutputBlockData } from '../../../types';
-import BlockTool from '../tools/block';
+import type { BlockId, BlockToolData, OutputBlockData } from '../../../types';
+import type BlockTool from '../tools/block';
+import type { StubData } from '../../tools/stub';
+import Block from '../block';
 
 /**
- * Editor.js Renderer Module
- *
- * @module Renderer
- * @author CodeX Team
- * @version 2.0.0
+ * Module that responsible for rendering Blocks on editor initialization
  */
 export default class Renderer extends Module {
   /**
-   * @typedef {object} RendererBlocks
-   * @property {string} type - tool name
-   * @property {object} data - tool data
-   */
-
-  /**
-   * @example
+   * Renders passed blocks as one batch
    *
-   * blocks: [
-   *   {
-   *     id   : 'oDe-EVrGWA',
-   *     type : 'paragraph',
-   *     data : {
-   *       text : 'Hello from Codex!'
-   *     }
-   *   },
-   *   {
-   *     id   : 'Ld5BJjJCHs',
-   *     type : 'paragraph',
-   *     data : {
-   *       text : 'Leave feedback if you like it!'
-   *     }
-   *   },
-   * ]
+   * @param blocksData - blocks to render
    */
+  public async render(blocksData: OutputBlockData[]): Promise<void> {
+    return new Promise((resolve) => {
+      const { Tools, BlockManager } = this.Editor;
 
-  /**
-   * Make plugin blocks from array of plugin`s data
-   *
-   * @param {OutputBlockData[]} blocks - blocks to render
-   */
-  public async render(blocks: OutputBlockData[]): Promise<void> {
-    const chainData = blocks.map((block) => ({ function: (): Promise<void> => this.insertBlock(block) }));
+      /**
+       * Create Blocks instances
+       */
+      const blocks = blocksData.map(({ type: tool, data, tunes, id }) => {
+        if (Tools.available.has(tool) === false) {
+          _.logLabeled(`Tool «${tool}» is not found. Check 'tools' property at the Editor.js config.`, 'warn');
 
-    /**
-     * Disable onChange callback on render to not to spam those events
-     */
-    this.Editor.ModificationsObserver.disable();
+          data = this.composeStubDataForTool(tool, data, id);
+          tool = Tools.stubTool;
+        }
 
-    const sequence = await _.sequence(chainData as _.ChainData[]);
+        let block: Block;
 
-    this.Editor.ModificationsObserver.enable();
+        try {
+          block = BlockManager.composeBlock({
+            id,
+            tool,
+            data,
+            tunes,
+          });
+        } catch (error) {
+          _.log(`Block «${tool}» skipped because of plugins error`, 'error', {
+            data,
+            error,
+          });
 
-    this.Editor.UI.checkEmptiness();
+          /**
+           * If tool throws an error during render, we should render stub instead of it
+           */
+          data = this.composeStubDataForTool(tool, data, id);
+          tool = Tools.stubTool;
 
-    return sequence;
-  }
+          block = BlockManager.composeBlock({
+            id,
+            tool,
+            data,
+            tunes,
+          });
+        }
 
-  /**
-   * Get plugin instance
-   * Add plugin instance to BlockManager
-   * Insert block to working zone
-   *
-   * @param {object} item - Block data to insert
-   * @returns {Promise<void>}
-   */
-  public async insertBlock(item: OutputBlockData): Promise<void> {
-    const { Tools, BlockManager } = this.Editor;
-    const { type: tool, data, tunes, id } = item;
-
-    if (Tools.available.has(tool)) {
-      try {
-        BlockManager.insert({
-          id,
-          tool,
-          data,
-          tunes,
-        });
-      } catch (error) {
-        _.log(`Block «${tool}» skipped because of plugins error`, 'warn', {
-          data,
-          error,
-        });
-        throw Error(error);
-      }
-    } else {
-      /** If Tool is unavailable, create stub Block for it */
-      const stubData = {
-        savedData: {
-          id,
-          type: tool,
-          data,
-        },
-        title: tool,
-      };
-
-      if (Tools.unavailable.has(tool)) {
-        const toolboxSettings = (Tools.unavailable.get(tool) as BlockTool).toolbox;
-        const toolboxTitle = toolboxSettings[0]?.title;
-
-        stubData.title = toolboxTitle || stubData.title;
-      }
-
-      const stub = BlockManager.insert({
-        id,
-        tool: Tools.stubTool,
-        data: stubData,
+        return block;
       });
 
-      stub.stretched = true;
+      /**
+       * Insert batch of Blocks
+       */
+      BlockManager.insertMany(blocks);
 
-      _.log(`Tool «${tool}» is not found. Check 'tools' property at your initial Editor.js config.`, 'warn');
+      /**
+       * Wait till browser will render inserted Blocks and resolve a promise
+       */
+      window.requestIdleCallback(() => {
+        resolve();
+      }, { timeout: 2000 });
+    });
+  }
+
+  /**
+   * Create data for the Stub Tool that will be used instead of unavailable tool
+   *
+   * @param tool - unavailable tool name to stub
+   * @param data - data of unavailable block
+   * @param [id] - id of unavailable block
+   */
+  private composeStubDataForTool(tool: string, data: BlockToolData, id?: BlockId): StubData {
+    const { Tools } = this.Editor;
+
+    let title = tool;
+
+    if (Tools.unavailable.has(tool)) {
+      const toolboxSettings = (Tools.unavailable.get(tool) as BlockTool).toolbox;
+
+      if (toolboxSettings !== undefined && toolboxSettings[0].title !== undefined) {
+        title = toolboxSettings[0].title;
+      }
     }
+
+    return {
+      savedData: {
+        id,
+        type: tool,
+        data,
+      },
+      title,
+    };
   }
 }
diff --git a/src/components/modules/saver.ts b/src/components/modules/saver.ts
index 28084f06..af8136d3 100644
--- a/src/components/modules/saver.ts
+++ b/src/components/modules/saver.ts
@@ -70,26 +70,11 @@ export default class Saver extends Module {
    * @returns {OutputData}
    */
   private makeOutput(allExtractedData): OutputData {
-    let totalTime = 0;
     const blocks = [];
 
-    _.log('[Editor.js saving]:', 'groupCollapsed');
-
-    allExtractedData.forEach(({ id, tool, data, tunes, time, isValid }) => {
-      totalTime += time;
-
-      /**
-       * Capitalize Tool name
-       */
-      _.log(`${tool.charAt(0).toUpperCase() + tool.slice(1)}`, 'group');
-
-      if (isValid) {
-        /** Group process info */
-        _.log(data);
-        _.log(undefined, 'groupEnd');
-      } else {
+    allExtractedData.forEach(({ id, tool, data, tunes, isValid }) => {
+      if (!isValid) {
         _.log(`Block «${tool}» skipped because saved data is invalid`);
-        _.log(undefined, 'groupEnd');
 
         return;
       }
@@ -113,9 +98,6 @@ export default class Saver extends Module {
       blocks.push(output);
     });
 
-    _.log('Total', 'log', totalTime);
-    _.log(undefined, 'groupEnd');
-
     return {
       time: +new Date(),
       blocks,
diff --git a/src/components/modules/toolbar/index.ts b/src/components/modules/toolbar/index.ts
index 4b8b6802..6f822380 100644
--- a/src/components/modules/toolbar/index.ts
+++ b/src/components/modules/toolbar/index.ts
@@ -103,8 +103,9 @@ export default class Toolbar extends Module<ToolbarNodes> {
 
   /**
    * Toolbox class instance
+   * It will be created in requestIdleCallback so it can be null in some period of time
    */
-  private toolboxInstance: Toolbox;
+  private toolboxInstance: Toolbox | null = null;
 
   /**
    * @class
@@ -155,18 +156,27 @@ export default class Toolbar extends Module<ToolbarNodes> {
    * Public interface for accessing the Toolbox
    */
   public get toolbox(): {
-    opened: boolean;
+    opened: boolean | undefined; // undefined is for the case when Toolbox is not initialized yet
     close: () => void;
     open: () => void;
     toggle: () => void;
-    hasFocus: () => boolean;
+    hasFocus: () => boolean | undefined;
     } {
     return {
-      opened: this.toolboxInstance.opened,
-      close: (): void => {
-        this.toolboxInstance.close();
+      opened: this.toolboxInstance?.opened,
+      close: () => {
+        this.toolboxInstance?.close();
       },
-      open: (): void => {
+      open: () => {
+        /**
+         * If Toolbox is not initialized yet, do nothing
+         */
+        if (this.toolboxInstance === null)  {
+          _.log('toolbox.open() called before initialization is finished', 'warn');
+
+          return;
+        }
+
         /**
          * Set current block to cover the case when the Toolbar showed near hovered Block but caret is set to another Block.
          */
@@ -174,8 +184,19 @@ export default class Toolbar extends Module<ToolbarNodes> {
 
         this.toolboxInstance.open();
       },
-      toggle: (): void => this.toolboxInstance.toggle(),
-      hasFocus: (): boolean => this.toolboxInstance.hasFocus(),
+      toggle: () => {
+        /**
+         * If Toolbox is not initialized yet, do nothing
+         */
+        if (this.toolboxInstance === null)  {
+          _.log('toolbox.toggle() called before initialization is finished', 'warn');
+
+          return;
+        }
+
+        this.toolboxInstance.toggle();
+      },
+      hasFocus: () => this.toolboxInstance?.hasFocus(),
     };
   }
 
@@ -210,8 +231,10 @@ export default class Toolbar extends Module<ToolbarNodes> {
    */
   public toggleReadOnly(readOnlyEnabled: boolean): void {
     if (!readOnlyEnabled) {
-      this.drawUI();
-      this.enableModuleBindings();
+      window.requestIdleCallback(() => {
+        this.drawUI();
+        this.enableModuleBindings();
+      }, { timeout: 2000 });
     } else {
       this.destroy();
       this.Editor.BlockSettings.destroy();
@@ -225,6 +248,15 @@ export default class Toolbar extends Module<ToolbarNodes> {
    * @param block - block to move Toolbar near it
    */
   public moveAndOpen(block: Block = this.Editor.BlockManager.currentBlock): void {
+    /**
+     * Some UI elements creates inside requestIdleCallback, so the can be not ready yet
+     */
+    if (this.toolboxInstance === null)  {
+      _.log('Can\'t open Toolbar since Editor initialization is not finished yet', 'warn');
+
+      return;
+    }
+
     /**
      * Close Toolbox when we move toolbar
      */
@@ -294,7 +326,7 @@ export default class Toolbar extends Module<ToolbarNodes> {
 
     /** Close components */
     this.blockActions.hide();
-    this.toolboxInstance.close();
+    this.toolboxInstance?.close();
     this.Editor.BlockSettings.close();
   }
 
@@ -454,7 +486,7 @@ export default class Toolbar extends Module<ToolbarNodes> {
      */
     this.Editor.BlockManager.currentBlock = this.hoveredBlock;
 
-    this.toolboxInstance.toggle();
+    this.toolboxInstance?.toggle();
   }
 
   /**
@@ -476,7 +508,7 @@ export default class Toolbar extends Module<ToolbarNodes> {
 
       this.settingsTogglerClicked();
 
-      if (this.toolboxInstance.opened) {
+      if (this.toolboxInstance?.opened) {
         this.toolboxInstance.close();
       }
 
@@ -496,7 +528,7 @@ export default class Toolbar extends Module<ToolbarNodes> {
         /**
          * Do not move toolbar if Block Settings or Toolbox opened
          */
-        if (this.Editor.BlockSettings.opened || this.toolboxInstance.opened) {
+        if (this.Editor.BlockSettings.opened || this.toolboxInstance?.opened) {
           return;
         }
 
diff --git a/src/components/modules/toolbar/inline.ts b/src/components/modules/toolbar/inline.ts
index 327e3dff..b032ed7a 100644
--- a/src/components/modules/toolbar/inline.ts
+++ b/src/components/modules/toolbar/inline.ts
@@ -122,7 +122,9 @@ export default class InlineToolbar extends Module<InlineToolbarNodes> {
    */
   public toggleReadOnly(readOnlyEnabled: boolean): void {
     if (!readOnlyEnabled) {
-      this.make();
+      window.requestIdleCallback(() => {
+        this.make();
+      }, { timeout: 2000 });
     } else {
       this.destroy();
       this.Editor.ConversionToolbar.destroy();
@@ -359,8 +361,11 @@ export default class InlineToolbar extends Module<InlineToolbarNodes> {
 
     /**
      * Recalculate initial width with all buttons
+     * We use RIC to prevent forced layout during editor initialization to make it faster
      */
-    this.recalculateWidth();
+    window.requestAnimationFrame(() => {
+      this.recalculateWidth();
+    });
 
     /**
      * Allow to leaf buttons by arrows / tab
diff --git a/src/components/modules/ui.ts b/src/components/modules/ui.ts
index 3a68889a..1378bd0c 100644
--- a/src/components/modules/ui.ts
+++ b/src/components/modules/ui.ts
@@ -22,7 +22,6 @@ interface UINodes {
   holder: HTMLElement;
   wrapper: HTMLElement;
   redactor: HTMLElement;
-  loader: HTMLElement;
 }
 
 /**
@@ -49,14 +48,13 @@ export default class UI extends Module<UINodes> {
    */
   public get CSS(): {
     editorWrapper: string; editorWrapperNarrow: string; editorZone: string; editorZoneHidden: string;
-    editorLoader: string; editorEmpty: string; editorRtlFix: string;
+    editorEmpty: string; editorRtlFix: string;
     } {
     return {
       editorWrapper: 'codex-editor',
       editorWrapperNarrow: 'codex-editor--narrow',
       editorZone: 'codex-editor__redactor',
       editorZoneHidden: 'codex-editor__redactor--hidden',
-      editorLoader: 'codex-editor__loader',
       editorEmpty: 'codex-editor--empty',
       editorRtlFix: 'codex-editor--rtl',
     };
@@ -115,23 +113,6 @@ export default class UI extends Module<UINodes> {
   // eslint-disable-next-line @typescript-eslint/no-magic-numbers
   }, 200);
 
-  /**
-   * Adds loader to editor while content is not ready
-   */
-  public addLoader(): void {
-    this.nodes.loader = $.make('div', this.CSS.editorLoader);
-    this.nodes.wrapper.prepend(this.nodes.loader);
-    this.nodes.redactor.classList.add(this.CSS.editorZoneHidden);
-  }
-
-  /**
-   * Removes loader when content has loaded
-   */
-  public removeLoader(): void {
-    this.nodes.loader.remove();
-    this.nodes.redactor.classList.remove(this.CSS.editorZoneHidden);
-  }
-
   /**
    * Making main interface
    */
@@ -146,11 +127,6 @@ export default class UI extends Module<UINodes> {
      */
     this.make();
 
-    /**
-     * Loader for rendering process
-     */
-    this.addLoader();
-
     /**
      * Load and append CSS
      */
@@ -277,6 +253,8 @@ export default class UI extends Module<UINodes> {
 
     /**
      * If Editor has injected into the narrow container, enable Narrow Mode
+     *
+     * @todo Forced layout. Get rid of this feature
      */
     if (this.nodes.holder.offsetWidth < this.contentRect.width) {
       this.nodes.wrapper.classList.add(this.CSS.editorWrapperNarrow);
@@ -684,12 +662,7 @@ export default class UI extends Module<UINodes> {
      * Select clicked Block as Current
      */
     try {
-      /**
-       * Renew Current Block. Use RAF to wait until Selection is set.
-       */
-      window.requestAnimationFrame(() => {
-        this.Editor.BlockManager.setCurrentBlockByChildNode(clickedNode);
-      });
+      this.Editor.BlockManager.setCurrentBlockByChildNode(clickedNode);
 
       /**
        * Highlight Current Node
diff --git a/src/components/polyfills.ts b/src/components/polyfills.ts
index d6f96aa1..20cb0cdb 100644
--- a/src/components/polyfills.ts
+++ b/src/components/polyfills.ts
@@ -136,3 +136,27 @@ if (!Element.prototype.scrollIntoViewIfNeeded) {
     }
   };
 }
+
+/**
+ * RequestIdleCallback polyfill (shims)
+ *
+ * @see https://developer.chrome.com/blog/using-requestidlecallback/
+ * @param cb - callback to be executed when the browser is idle
+ */
+window.requestIdleCallback = window.requestIdleCallback || function (cb) {
+  const start = Date.now();
+
+  return setTimeout(function () {
+    cb({
+      didTimeout: false,
+      timeRemaining: function () {
+        // eslint-disable-next-line @typescript-eslint/no-magic-numbers
+        return Math.max(0, 50 - (Date.now() - start));
+      },
+    });
+  }, 1);
+};
+
+window.cancelIdleCallback = window.cancelIdleCallback || function (id) {
+  clearTimeout(id);
+};
diff --git a/src/components/selection.ts b/src/components/selection.ts
index d38dd841..fe5f961a 100644
--- a/src/components/selection.ts
+++ b/src/components/selection.ts
@@ -225,7 +225,7 @@ export default class SelectionUtils {
    *
    * @param selection - Selection object to get Range from
    */
-  public static getRangeFromSelection(selection: Selection): Range {
+  public static getRangeFromSelection(selection: Selection): Range | null {
     return selection && selection.rangeCount ? selection.getRangeAt(0) : null;
   }
 
diff --git a/src/components/utils.ts b/src/components/utils.ts
index a0bd2666..6e30817b 100644
--- a/src/components/utils.ts
+++ b/src/components/utils.ts
@@ -311,6 +311,7 @@ export function isPrintableKey(keyCode: number): boolean {
  * @param {Function} success - success callback
  * @param {Function} fallback - callback that fires in case of errors
  * @returns {Promise}
+ * @deprecated use PromiseQueue.ts instead
  */
 export async function sequence(
   chains: ChainData[],
diff --git a/src/components/utils/events.ts b/src/components/utils/events.ts
index 3c748a2c..2599f0b7 100644
--- a/src/components/utils/events.ts
+++ b/src/components/utils/events.ts
@@ -94,6 +94,12 @@ export default class EventsDispatcher<EventMap> {
    * @param callback - event handler
    */
   public off<Name extends keyof EventMap>(eventName: Name, callback: Listener<EventMap[Name]>): void {
+    if (this.subscribers[eventName] === undefined) {
+      console.warn(`EventDispatcher .off(): there is no subscribers for event "${eventName.toString()}". Probably, .off() called before .on()`);
+
+      return;
+    }
+
     for (let i = 0; i < this.subscribers[eventName].length; i++) {
       if (this.subscribers[eventName][i] === callback) {
         delete this.subscribers[eventName][i];
@@ -107,6 +113,6 @@ export default class EventsDispatcher<EventMap> {
    * clears subscribers list
    */
   public destroy(): void {
-    this.subscribers = null;
+    this.subscribers = {} as Subscriptions<EventMap>;
   }
 }
diff --git a/src/components/utils/promise-queue.ts b/src/components/utils/promise-queue.ts
new file mode 100644
index 00000000..082f44a2
--- /dev/null
+++ b/src/components/utils/promise-queue.ts
@@ -0,0 +1,28 @@
+/**
+ * Class allows to make a queue of async jobs and wait until they all will be finished one by one
+ *
+ * @example const queue = new PromiseQueue();
+ *            queue.add(async () => { ... });
+ *            queue.add(async () => { ... });
+ *            await queue.completed;
+ */
+export default class PromiseQueue {
+  /**
+   * Queue of promises to be executed
+   */
+  public completed = Promise.resolve();
+
+  /**
+   * Add new promise to queue
+   *
+   * @param operation - promise should be added to queue
+   */
+  public add(operation: (value: void) => void | PromiseLike<void>): Promise<void> {
+    return new Promise((resolve, reject) => {
+      this.completed = this.completed
+        .then(operation)
+        .then(resolve)
+        .catch(reject);
+    });
+  }
+}
diff --git a/src/styles/stub.css b/src/styles/stub.css
index e2f3bc50..36a87635 100644
--- a/src/styles/stub.css
+++ b/src/styles/stub.css
@@ -1,26 +1,25 @@
 .ce-stub {
   display: flex;
   align-items: center;
-  justify-content: center;
-  width: 100%;
-  padding: 3.5em 0;
-  margin: 17px 0;
-  border-radius: 3px;
-  background: #fcf7f7;
-  color: #b46262;
+  padding: 12px 18px;
+  margin: 10px 0;
+  border-radius: 10px;
+  background: var(--bg-light);
+  border: 1px solid var(--color-line-gray);
+  color: var(--grayText);
+  font-size: 14px;
+
+  svg {
+    width: var(--icon-size);
+    height: var(--icon-size);
+  }
 
   &__info {
-    margin-left: 20px;
+    margin-left: 14px;
   }
 
   &__title {
-    margin-bottom: 3px;
-    font-weight: 600;
-    font-size: 18px;
+    font-weight: 500;
     text-transform: capitalize;
   }
-
-  &__subtitle {
-    font-size: 16px;
-  }
 }
diff --git a/src/styles/ui.css b/src/styles/ui.css
index 9032e791..d84237b5 100644
--- a/src/styles/ui.css
+++ b/src/styles/ui.css
@@ -11,10 +11,6 @@
   }
 
   &__redactor {
-    &--hidden {
-      display: none;
-    }
-
     /**
      * Workaround firefox bug: empty content editable elements has collapsed height
      * https://bugzilla.mozilla.org/show_bug.cgi?id=1098151#c18
@@ -46,28 +42,6 @@
     }
   }
 
-  &__loader {
-    position: relative;
-    height: 30vh;
-
-    &::before {
-      content: '';
-      position: absolute;
-      left: 50%;
-      top: 50%;
-      width: 30px;
-      height: 30px;
-      margin-top: -15px;
-      margin-left: -15px;
-      border-radius: 50%;
-      border: 2px solid var(--color-gray-border);
-      border-top-color: transparent;
-      box-sizing: border-box;
-      animation: editor-loader-spin 800ms infinite linear;
-      will-change: transform;
-    }
-  }
-
   &-copyable {
     position: absolute;
     height: 1px;
@@ -107,29 +81,21 @@
   path {
     stroke: currentColor;
   }
+
+
+  /**
+  * Set color for native selection
+  */
+  ::selection{
+    background-color: var(--inlineSelectionColor);
+  }
 }
 
-/**
- * Set color for native selection
- */
-::selection{
-  background-color: var(--inlineSelectionColor);
-}
 
 .codex-editor--toolbox-opened [contentEditable=true][data-placeholder]:focus::before {
   opacity: 0 !important;
 }
 
-@keyframes editor-loader-spin {
-  0% {
-    transform: rotate(0deg);
-  }
-
-  100% {
-    transform: rotate(360deg);
-  }
-}
-
 .ce-scroll-locked {
   overflow: hidden;
 }
diff --git a/src/tools/stub/index.ts b/src/tools/stub/index.ts
index d5cd1be8..be75295f 100644
--- a/src/tools/stub/index.ts
+++ b/src/tools/stub/index.ts
@@ -1,5 +1,6 @@
 import $ from '../../components/dom';
 import { API, BlockTool, BlockToolConstructorOptions, BlockToolData } from '../../../types';
+import { IconWarning } from '@codexteam/icons';
 
 export interface StubData extends BlockToolData {
   title: string;
@@ -92,7 +93,7 @@ export default class Stub implements BlockTool {
    */
   private make(): HTMLElement {
     const wrapper = $.make('div', this.CSS.wrapper);
-    const icon = `<svg xmlns="http://www.w3.org/2000/svg" width="52" height="52" viewBox="0 0 52 52"><path fill="#D76B6B" fill-rule="nonzero" d="M26 52C11.64 52 0 40.36 0 26S11.64 0 26 0s26 11.64 26 26-11.64 26-26 26zm0-3.25c12.564 0 22.75-10.186 22.75-22.75S38.564 3.25 26 3.25 3.25 13.436 3.25 26 13.436 48.75 26 48.75zM15.708 33.042a2.167 2.167 0 1 1 0-4.334 2.167 2.167 0 0 1 0 4.334zm23.834 0a2.167 2.167 0 1 1 0-4.334 2.167 2.167 0 0 1 0 4.334zm-15.875 5.452a1.083 1.083 0 1 1-1.834-1.155c1.331-2.114 3.49-3.179 6.334-3.179 2.844 0 5.002 1.065 6.333 3.18a1.083 1.083 0 1 1-1.833 1.154c-.913-1.45-2.366-2.167-4.5-2.167s-3.587.717-4.5 2.167z"/></svg>`;
+    const icon = IconWarning;
     const infoContainer = $.make('div', this.CSS.info);
     const title = $.make('div', this.CSS.title, {
       textContent: this.title,
diff --git a/test/cypress/.eslintrc b/test/cypress/.eslintrc
index 8b90cf86..6671eb30 100644
--- a/test/cypress/.eslintrc
+++ b/test/cypress/.eslintrc
@@ -11,7 +11,9 @@
         "plugin:chai-friendly/recommended"
     ],
     "rules": {
-        "cypress/require-data-selectors": 2
+        "cypress/require-data-selectors": 2,
+        "cypress/no-unnecessary-waiting": 0,
+        "@typescript-eslint/no-magic-numbers": 0
     },
     "globals": {
         "EditorJS": true
diff --git a/test/cypress/support/commands.ts b/test/cypress/support/commands.ts
index 8f19ca2e..b6ca36eb 100644
--- a/test/cypress/support/commands.ts
+++ b/test/cypress/support/commands.ts
@@ -61,7 +61,7 @@ Cypress.Commands.add('paste', {
 
   subject[0].dispatchEvent(pasteEvent);
 
-  return subject;
+  cy.wait(200); // wait a little since some tools (paragraph) could have async hydration
 });
 
 /**
@@ -79,7 +79,6 @@ Cypress.Commands.add('copy', { prevSubject: true }, (subject) => {
   }), {
     clipboardData: {
       setData: (type: string, data: any): void => {
-        console.log(type, data);
         clipboardData[type] = data;
       },
     },
@@ -105,7 +104,6 @@ Cypress.Commands.add('cut', { prevSubject: true }, (subject) => {
   }), {
     clipboardData: {
       setData: (type: string, data: any): void => {
-        console.log(type, data);
         clipboardData[type] = data;
       },
     },
@@ -122,9 +120,10 @@ Cypress.Commands.add('cut', { prevSubject: true }, (subject) => {
  * @param data — data to render
  */
 Cypress.Commands.add('render', { prevSubject: true }, (subject: EditorJS, data: OutputData) => {
-  subject.render(data);
-
-  return cy.wrap(subject);
+  return cy.wrap(subject.render(data))
+    .then(() => {
+      return cy.wrap(subject);
+    });
 });
 
 
@@ -154,5 +153,5 @@ Cypress.Commands.add('selectText', {
   document.getSelection().removeAllRanges();
   document.getSelection().addRange(range);
 
-  return subject;
+  return cy.wrap(subject);
 });
diff --git a/test/cypress/support/index.ts b/test/cypress/support/index.ts
index 6eb582ec..a3a0662a 100644
--- a/test/cypress/support/index.ts
+++ b/test/cypress/support/index.ts
@@ -7,6 +7,9 @@
  */
 
 import '@cypress/code-coverage/support';
+import installLogsCollector from 'cypress-terminal-report/src/installLogsCollector';
+
+installLogsCollector();
 
 /**
  * File with the helpful commands
diff --git a/test/cypress/tests/api/blocks.cy.ts b/test/cypress/tests/api/blocks.cy.ts
index 62c49fcc..13229cca 100644
--- a/test/cypress/tests/api/blocks.cy.ts
+++ b/test/cypress/tests/api/blocks.cy.ts
@@ -63,9 +63,7 @@ describe('api.blocks', () => {
     it('should update block in DOM', () => {
       cy.createEditor({
         data: editorDataMock,
-      }).as('editorInstance');
-
-      cy.get<EditorJS>('@editorInstance').then(async (editor) => {
+      }).then((editor) => {
         const idToUpdate = firstBlock.id;
         const newBlockData = {
           text: 'Updated text',
@@ -75,10 +73,7 @@ describe('api.blocks', () => {
 
         cy.get('[data-cy=editorjs]')
           .get('div.ce-block')
-          .invoke('text')
-          .then(blockText => {
-            expect(blockText).to.be.eq(newBlockData.text);
-          });
+          .should('have.text', newBlockData.text);
       });
     });
 
@@ -88,9 +83,7 @@ describe('api.blocks', () => {
     it('should update block in saved data', () => {
       cy.createEditor({
         data: editorDataMock,
-      }).as('editorInstance');
-
-      cy.get<EditorJS>('@editorInstance').then(async (editor) => {
+      }).then((editor) => {
         const idToUpdate = firstBlock.id;
         const newBlockData = {
           text: 'Updated text',
@@ -98,10 +91,14 @@ describe('api.blocks', () => {
 
         editor.blocks.update(idToUpdate, newBlockData);
 
-        const output = await editor.save();
-        const text = output.blocks[0].data.text;
+        // wait a little since some tools (paragraph) could have async hydration
+        cy.wait(100).then(() => {
+          editor.save().then((output) => {
+            const text = output.blocks[0].data.text;
 
-        expect(text).to.be.eq(newBlockData.text);
+            expect(text).to.be.eq(newBlockData.text);
+          });
+        });
       });
     });
 
@@ -111,9 +108,7 @@ describe('api.blocks', () => {
     it('shouldn\'t update any block if not-existed id passed', () => {
       cy.createEditor({
         data: editorDataMock,
-      }).as('editorInstance');
-
-      cy.get<EditorJS>('@editorInstance').then(async (editor) => {
+      }).then((editor) => {
         const idToUpdate = 'wrong-id-123';
         const newBlockData = {
           text: 'Updated text',
@@ -138,9 +133,7 @@ describe('api.blocks', () => {
     it('should preserve block id if it is passed', function () {
       cy.createEditor({
         data: editorDataMock,
-      }).as('editorInstance');
-
-      cy.get<EditorJS>('@editorInstance').then(async (editor) => {
+      }).then((editor) => {
         const type = 'paragraph';
         const data = { text: 'codex' };
         const config = undefined;
@@ -157,6 +150,53 @@ describe('api.blocks', () => {
     });
   });
 
+  /**
+   * api.blocks.insertMany(blocks, index)
+   */
+  describe('.insertMany()', function () {
+    it('should insert several blocks to passed index', function () {
+      cy.createEditor({
+        data: {
+          blocks: [
+            {
+              type: 'paragraph',
+              data: { text: 'first block' },
+            }
+          ],
+        },
+      }).then((editor) => {
+        const index = 0;
+
+        cy.wrap(editor.blocks.insertMany([
+          {
+            type: 'paragraph',
+            data: { text: 'inserting block #1' },
+          },
+          {
+            type: 'paragraph',
+            data: { text: 'inserting block #2' },
+          },
+        ], index)); // paste to the 0 index
+
+        cy.get('[data-cy=editorjs]')
+          .find('.ce-block')
+          .each(($el, i) => {
+            switch (i) {
+              case 0:
+                cy.wrap($el).should('have.text', 'inserting block #1');
+                break;
+              case 1:
+                cy.wrap($el).should('have.text', 'inserting block #2');
+                break;
+              case 2:
+                cy.wrap($el).should('have.text', 'first block');
+                break;
+            }
+          });
+      });
+    });
+  });
+
   describe('.convert()', function () {
     it('should convert a Block to another type if original Tool has "conversionConfig.export" and target Tool has "conversionConfig.import"', function () {
       /**
@@ -202,42 +242,31 @@ describe('api.blocks', () => {
             existingBlock,
           ],
         },
-      }).as('editorInstance');
+      }).then((editor) => {
+        const { convert } = editor.blocks;
 
-      /**
-       * Call the 'convert' api method
-       */
-      cy.get<EditorJS>('@editorInstance')
-        .then(async (editor) => {
-          const { convert } = editor.blocks;
+        convert(existingBlock.id, 'convertableTool');
 
-          convert(existingBlock.id, 'convertableTool');
-        });
-
-      // eslint-disable-next-line cypress/no-unnecessary-waiting, @typescript-eslint/no-magic-numbers -- wait for block to be converted
-      cy.wait(100);
-
-      /**
-       * Check that block was converted
-       */
-      cy.get<EditorJS>('@editorInstance')
-        .then(async (editor) => {
-          const { blocks } = await editor.save();
-
-          expect(blocks.length).to.eq(1);
-          expect(blocks[0].type).to.eq('convertableTool');
-          expect(blocks[0].data.text).to.eq(existingBlock.data.text);
+        // wait for block to be converted
+        cy.wait(100).then(() => {
+          /**
+           * Check that block was converted
+           */
+          editor.save().then(( { blocks }) => {
+            expect(blocks.length).to.eq(1);
+            expect(blocks[0].type).to.eq('convertableTool');
+            expect(blocks[0].data.text).to.eq(existingBlock.data.text);
+          });
         });
+      });
     });
 
     it('should throw an error if nonexisting Block id passed', function () {
-      cy.createEditor({}).as('editorInstance');
-
-      /**
-       * Call the 'convert' api method with nonexisting Block id
-       */
-      cy.get<EditorJS>('@editorInstance')
-        .then(async (editor) => {
+      cy.createEditor({})
+        .then((editor) => {
+          /**
+           * Call the 'convert' api method with nonexisting Block id
+           */
           const fakeId = 'WRNG_ID';
           const { convert } = editor.blocks;
 
@@ -262,20 +291,17 @@ describe('api.blocks', () => {
             existingBlock,
           ],
         },
-      }).as('editorInstance');
+      }).then((editor) => {
+        /**
+         * Call the 'convert' api method with nonexisting tool name
+         */
+        const nonexistingToolName = 'WRNG_TOOL_NAME';
+        const { convert } = editor.blocks;
 
-      /**
-       * Call the 'convert' api method with nonexisting tool name
-       */
-      cy.get<EditorJS>('@editorInstance')
-        .then(async (editor) => {
-          const nonexistingToolName = 'WRNG_TOOL_NAME';
-          const { convert } = editor.blocks;
+        const exec = (): void => convert(existingBlock.id, nonexistingToolName);
 
-          const exec = (): void => convert(existingBlock.id, nonexistingToolName);
-
-          expect(exec).to.throw(`Block Tool with type "${nonexistingToolName}" not found`);
-        });
+        expect(exec).to.throw(`Block Tool with type "${nonexistingToolName}" not found`);
+      });
     });
 
     it('should throw an error if some tool does not provide "conversionConfig"', function () {
@@ -304,19 +330,16 @@ describe('api.blocks', () => {
             existingBlock,
           ],
         },
-      }).as('editorInstance');
+      }).then((editor) => {
+        /**
+         * Call the 'convert' api method with tool that does not provide "conversionConfig"
+         */
+        const { convert } = editor.blocks;
 
-      /**
-       * Call the 'convert' api method with tool that does not provide "conversionConfig"
-       */
-      cy.get<EditorJS>('@editorInstance')
-        .then(async (editor) => {
-          const { convert } = editor.blocks;
+        const exec = (): void => convert(existingBlock.id, 'nonConvertableTool');
 
-          const exec = (): void => convert(existingBlock.id, 'nonConvertableTool');
-
-          expect(exec).to.throw(`Conversion from "paragraph" to "nonConvertableTool" is not possible. NonConvertableTool tool(s) should provide a "conversionConfig"`);
-        });
+        expect(exec).to.throw(`Conversion from "paragraph" to "nonConvertableTool" is not possible. NonConvertableTool tool(s) should provide a "conversionConfig"`);
+      });
     });
   });
 });
diff --git a/test/cypress/tests/block-ids.cy.ts b/test/cypress/tests/block-ids.cy.ts
index 19046137..3f4b001c 100644
--- a/test/cypress/tests/block-ids.cy.ts
+++ b/test/cypress/tests/block-ids.cy.ts
@@ -1,23 +1,16 @@
-/* eslint-disable @typescript-eslint/no-explicit-any */
 import Header from '@editorjs/header';
 import { nanoid } from 'nanoid';
+import type EditorJS from '../../../types/index';
+
 
 describe('Block ids', () => {
-  beforeEach(function () {
+  it('Should generate unique block ids for new blocks', () => {
     cy.createEditor({
       tools: {
         header: Header,
       },
     }).as('editorInstance');
-  });
 
-  afterEach(function () {
-    if (this.editorInstance) {
-      this.editorInstance.destroy();
-    }
-  });
-
-  it('Should generate unique block ids for new blocks', () => {
     cy.get('[data-cy=editorjs]')
       .get('div.ce-block')
       .click()
@@ -42,8 +35,8 @@ describe('Block ids', () => {
       .click()
       .type('Header');
 
-    cy.get('@editorInstance')
-      .then(async (editor: any) => {
+    cy.get<EditorJS>('@editorInstance')
+      .then(async (editor) => {
         const data = await editor.save();
 
         data.blocks.forEach(block => {
@@ -53,6 +46,9 @@ describe('Block ids', () => {
   });
 
   it('should preserve passed ids', () => {
+    cy.createEditor({})
+      .as('editorInstance');
+
     const blocks = [
       {
         id: nanoid(),
@@ -70,19 +66,13 @@ describe('Block ids', () => {
       },
     ];
 
-    cy.get('@editorInstance')
+    cy.get<EditorJS>('@editorInstance')
       .render({
         blocks,
       });
 
-    cy.get('[data-cy=editorjs]')
-      .get('div.ce-block')
-      .first()
-      .click()
-      .type('{movetoend} Some more text');
-
-    cy.get('@editorInstance')
-      .then(async (editor: any) => {
+    cy.get<EditorJS>('@editorInstance')
+      .then(async (editor) => {
         const data = await editor.save();
 
         data.blocks.forEach((block, index) => {
@@ -92,6 +82,9 @@ describe('Block ids', () => {
   });
 
   it('should preserve passed ids if blocks were added', () => {
+    cy.createEditor({})
+      .as('editorInstance');
+
     const blocks = [
       {
         id: nanoid(),
@@ -109,7 +102,7 @@ describe('Block ids', () => {
       },
     ];
 
-    cy.get('@editorInstance')
+    cy.get<EditorJS>('@editorInstance')
       .render({
         blocks,
       });
@@ -122,16 +115,20 @@ describe('Block ids', () => {
       .next()
       .type('Middle block');
 
-    cy.get('@editorInstance')
-      .then(async (editor: any) => {
-        const data = await editor.save();
-
-        expect(data.blocks[0].id).to.eq(blocks[0].id);
-        expect(data.blocks[2].id).to.eq(blocks[1].id);
+    cy.get<EditorJS>('@editorInstance')
+      .then(async (editor) => {
+        cy.wrap(await editor.save())
+          .then((data) => {
+            expect(data.blocks[0].id).to.eq(blocks[0].id);
+            expect(data.blocks[2].id).to.eq(blocks[1].id);
+          });
       });
   });
 
   it('should be stored at the Block wrapper\'s data-id attribute', () => {
+    cy.createEditor({})
+      .as('editorInstance');
+
     const blocks = [
       {
         id: nanoid(),
@@ -149,7 +146,7 @@ describe('Block ids', () => {
       },
     ];
 
-    cy.get('@editorInstance')
+    cy.get<EditorJS>('@editorInstance')
       .render({
         blocks,
       });
diff --git a/test/cypress/tests/copy-paste.cy.ts b/test/cypress/tests/copy-paste.cy.ts
index 87011d04..132c1c90 100644
--- a/test/cypress/tests/copy-paste.cy.ts
+++ b/test/cypress/tests/copy-paste.cy.ts
@@ -1,51 +1,44 @@
 import Header from '@editorjs/header';
 import Image from '@editorjs/simple-image';
 import * as _ from '../../../src/components/utils';
-import EditorJS, { BlockTool, BlockToolData } from '../../../types';
+import { BlockTool, BlockToolData } from '../../../types';
 import $ from '../../../src/components/dom';
 
 describe('Copy pasting from Editor', function () {
-  beforeEach(function () {
-    cy.createEditor({
-      tools: {
-        header: Header,
-        image: Image,
-      },
-    }).as('editorInstance');
-  });
-
-  afterEach(function () {
-    if (this.editorInstance && this.editorInstance.destroy) {
-      this.editorInstance.destroy();
-    }
-  });
-
   context('pasting', function () {
     it('should paste plain text', function () {
-      // eslint-disable-next-line cypress/no-unnecessary-waiting
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
+        .as('block')
         .click()
         .paste({
           // eslint-disable-next-line @typescript-eslint/naming-convention
           'text/plain': 'Some plain text',
-        })
-        .wait(0)
-        .should('contain', 'Some plain text');
+        });
+
+      cy.get('@block').should('contain', 'Some plain text');
     });
 
     it('should paste inline html data', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
+        .as('block')
         .click()
         .paste({
           // eslint-disable-next-line @typescript-eslint/naming-convention
           'text/html': '<p><b>Some text</b></p>',
-        })
-        .should('contain.html', '<b>Some text</b>');
+        });
+
+      cy.get('@block').should('contain.html', '<b>Some text</b>');
     });
 
     it('should paste several blocks if plain text contains new lines', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -63,6 +56,8 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should paste several blocks if html contains several paragraphs', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -80,6 +75,8 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should paste using custom data type', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -110,6 +107,12 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should parse block tags', function () {
+      cy.createEditor({
+        tools: {
+          header: Header,
+        },
+      });
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -128,6 +131,12 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should parse pattern', function () {
+      cy.createEditor({
+        tools: {
+          image: Image,
+        },
+      });
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -143,12 +152,6 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should not prevent default behaviour if block\'s paste config equals false', function () {
-      /**
-       * Destroy default Editor to render custom one with different tools
-       */
-      cy.get('@editorInstance')
-        .then((editorInstance: unknown) => (editorInstance as EditorJS).destroy());
-
       const onPasteStub = cy.stub().as('onPaste');
 
       /**
@@ -182,7 +185,8 @@ describe('Copy pasting from Editor', function () {
         tools: {
           blockToolWithPasteHandler: BlockToolWithPasteHandler,
         },
-      }).as('editorInstanceWithBlockToolWithPasteHandler');
+      })
+        .as('editorInstanceWithBlockToolWithPasteHandler');
 
       cy.get('@editorInstanceWithBlockToolWithPasteHandler')
         .render({
@@ -192,7 +196,8 @@ describe('Copy pasting from Editor', function () {
               data: {},
             },
           ],
-        });
+        })
+        .wait(100);
 
       cy.get('@editorInstanceWithBlockToolWithPasteHandler')
         .get('div.ce-block-with-disabled-prevent-default')
@@ -211,6 +216,8 @@ describe('Copy pasting from Editor', function () {
 
   context('copying', function () {
     it('should copy inline fragment', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -225,6 +232,8 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should copy several blocks', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -247,7 +256,6 @@ describe('Copy pasting from Editor', function () {
           /**
            * Need to wait for custom data as it is set asynchronously
            */
-          // eslint-disable-next-line cypress/no-unnecessary-waiting
           cy.wait(0).then(function () {
             expect(clipboardData['application/x-editor-js']).not.to.be.undefined;
 
@@ -264,6 +272,8 @@ describe('Copy pasting from Editor', function () {
 
   context('cutting', function () {
     it('should cut inline fragment', function () {
+      cy.createEditor({});
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -278,15 +288,25 @@ describe('Copy pasting from Editor', function () {
     });
 
     it('should cut several blocks', function () {
-      cy.get('[data-cy=editorjs]')
-        .get('div.ce-block')
-        .click()
-        .type('First block{enter}');
+      cy.createEditor({
+        data: {
+          blocks: [
+            {
+              type: 'paragraph',
+              data: { text: 'First block' },
+            },
+            {
+              type: 'paragraph',
+              data: { text: 'Second block' },
+            },
+          ],
+        },
+      });
 
       cy.get('[data-cy=editorjs')
         .get('div.ce-block')
-        .next()
-        .type('Second block')
+        .last()
+        .click()
         .type('{movetostart}')
         .trigger('keydown', {
           shiftKey: true,
@@ -300,7 +320,6 @@ describe('Copy pasting from Editor', function () {
           /**
            * Need to wait for custom data as it is set asynchronously
            */
-          // eslint-disable-next-line cypress/no-unnecessary-waiting
           cy.wait(0).then(function () {
             expect(clipboardData['application/x-editor-js']).not.to.be.undefined;
 
@@ -320,15 +339,23 @@ describe('Copy pasting from Editor', function () {
 
     it('should cut lots of blocks', function () {
       const numberOfBlocks = 50;
+      const blocks = [];
 
       for (let i = 0; i < numberOfBlocks; i++) {
-        cy.get('[data-cy=editorjs]')
-          .get('div.ce-block')
-          .last()
-          .click()
-          .type(`Block ${i}{enter}`);
+        blocks.push({
+          type: 'paragraph',
+          data: {
+            text: `Block ${i}`,
+          },
+        });
       }
 
+      cy.createEditor({
+        data: {
+          blocks,
+        },
+      });
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .first()
@@ -340,13 +367,12 @@ describe('Copy pasting from Editor', function () {
           /**
            * Need to wait for custom data as it is set asynchronously
            */
-          // eslint-disable-next-line cypress/no-unnecessary-waiting
           cy.wait(0).then(function () {
             expect(clipboardData['application/x-editor-js']).not.to.be.undefined;
 
             const data = JSON.parse(clipboardData['application/x-editor-js']);
 
-            expect(data.length).to.eq(numberOfBlocks + 1);
+            expect(data.length).to.eq(numberOfBlocks);
           });
         });
     });
diff --git a/test/cypress/tests/i18n.cy.ts b/test/cypress/tests/i18n.cy.ts
index 621bd25e..cec4f2c0 100644
--- a/test/cypress/tests/i18n.cy.ts
+++ b/test/cypress/tests/i18n.cy.ts
@@ -127,7 +127,8 @@ describe('Editor i18n', () => {
             toolNames: toolNamesDictionary,
           },
         },
-      }).as('editorInstance');
+      });
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click();
diff --git a/test/cypress/tests/modules/BlockEvents/Backspace.cy.ts b/test/cypress/tests/modules/BlockEvents/Backspace.cy.ts
index 640d1523..ac988a0b 100644
--- a/test/cypress/tests/modules/BlockEvents/Backspace.cy.ts
+++ b/test/cypress/tests/modules/BlockEvents/Backspace.cy.ts
@@ -1,12 +1,14 @@
 import type EditorJS from '../../../../../types/index';
+import Chainable = Cypress.Chainable;
+
 
 /**
  * Creates Editor instance with list of Paragraph blocks of passed texts
  *
  * @param textBlocks - list of texts for Paragraph blocks
  */
-function createEditorWithTextBlocks(textBlocks: string[]): void {
-  cy.createEditor({
+function createEditorWithTextBlocks(textBlocks: string[]): Chainable<EditorJS> {
+  return cy.createEditor({
     data: {
       blocks: textBlocks.map((text) => ({
         type: 'paragraph',
diff --git a/test/cypress/tests/modules/BlockEvents/Enter.cy.ts b/test/cypress/tests/modules/BlockEvents/Enter.cy.ts
index 7469d187..3dde743e 100644
--- a/test/cypress/tests/modules/BlockEvents/Enter.cy.ts
+++ b/test/cypress/tests/modules/BlockEvents/Enter.cy.ts
@@ -13,8 +13,6 @@ describe('Enter keydown', function () {
       },
     });
 
-
-    // eslint-disable-next-line cypress/no-unnecessary-waiting
     cy.get('[data-cy=editorjs]')
       .find('.ce-paragraph')
       .click()
@@ -22,7 +20,6 @@ describe('Enter keydown', function () {
       .wait(0)
       .type('{enter}');
 
-
     cy.get('[data-cy=editorjs]')
       .find('div.ce-block')
       .then((blocks) => {
diff --git a/test/cypress/tests/modules/Renderer.cy.ts b/test/cypress/tests/modules/Renderer.cy.ts
new file mode 100644
index 00000000..6ccf164e
--- /dev/null
+++ b/test/cypress/tests/modules/Renderer.cy.ts
@@ -0,0 +1,149 @@
+import ToolMock from '../../fixtures/tools/ToolMock';
+
+describe('Renderer module', function () {
+  it('should not cause onChange firing during initial rendering', function () {
+    const config = {
+      data: {
+        blocks: [
+          {
+            type: 'paragraph',
+            data: {
+              text: 'some text',
+            },
+          },
+          {
+            type: 'paragraph',
+            data: {
+              text: 'some other text',
+            },
+          },
+        ],
+      },
+      // eslint-disable-next-line @typescript-eslint/no-empty-function
+      onChange: () => {},
+    };
+
+    cy.createEditor(config)
+      .as('editorInstance');
+
+    cy.spy(config, 'onChange').as('onChange');
+
+    cy.get('@onChange').should('not.be.called');
+  });
+
+  it('should show Stub block if block tool is not registered', function () {
+    cy.createEditor({
+      data: {
+        blocks: [
+          {
+            type: 'paragraph',
+            data: {
+              text: 'some text',
+            },
+          },
+          {
+            type: 'non-existing tool',
+            data: {},
+          },
+          {
+            type: 'paragraph',
+            data: {
+              text: 'some other text',
+            },
+          },
+        ],
+      },
+    })
+      .as('editorInstance');
+
+    cy.get('[data-cy=editorjs]')
+      .find('.ce-block')
+      .should('have.length', 3);
+
+    cy.get('[data-cy=editorjs]')
+      .find('.ce-block')
+      .each(($el, index) => {
+        /**
+         * Check that the second block is stub
+         */
+        if (index === 1) {
+          cy.wrap($el)
+            .find('.ce-stub')
+            .should('have.length', 1);
+
+          /**
+           * Tool title displayed
+           */
+          cy.wrap($el)
+            .find('.ce-stub__title')
+            .should('have.text', 'non-existing tool');
+        }
+      });
+  });
+
+  it('should show Stub block if block tool throws error during construction', function () {
+    /**
+     * Mock of tool that triggers error during construction
+     */
+    class ToolWithError extends ToolMock {
+      /**
+       * @param options - tool options
+       */
+      constructor(options) {
+        super(options);
+        throw new Error('Tool error');
+      }
+    }
+
+    cy.createEditor({
+      data: {
+        blocks: [
+          {
+            type: 'paragraph',
+            data: {
+              text: 'some text',
+            },
+          },
+          {
+            type: 'failedTool',
+            data: {},
+          },
+          {
+            type: 'paragraph',
+            data: {
+              text: 'some other text',
+            },
+          },
+        ],
+      },
+      tools: {
+        failedTool: ToolWithError,
+      },
+    })
+      .as('editorInstance');
+
+    cy.get('[data-cy=editorjs]')
+      .find('.ce-block')
+      .should('have.length', 3);
+
+    cy.get('[data-cy=editorjs]')
+      .find('.ce-block')
+      .each(($el, index) => {
+        /**
+         * Check that the second block is stub
+         */
+        if (index === 1) {
+          cy.wrap($el)
+            .find('.ce-stub')
+            .should('have.length', 1);
+
+          /**
+           * Tool title displayed
+           */
+          cy.wrap($el)
+            .find('.ce-stub__title')
+            .should('have.text', 'failedTool');
+        }
+      });
+  });
+});
diff --git a/test/cypress/tests/onchange.cy.ts b/test/cypress/tests/onchange.cy.ts
index 13c4fccf..79d8dc7d 100644
--- a/test/cypress/tests/onchange.cy.ts
+++ b/test/cypress/tests/onchange.cy.ts
@@ -5,6 +5,7 @@ import { BlockAddedMutationType } from '../../../types/events/block/BlockAdded';
 import { BlockChangedMutationType } from '../../../types/events/block/BlockChanged';
 import { BlockRemovedMutationType } from '../../../types/events/block/BlockRemoved';
 import { BlockMovedMutationType } from '../../../types/events/block/BlockMoved';
+import type EditorJS from '../../../types/index';
 
 
 /**
@@ -132,7 +133,6 @@ describe('onChange callback', () => {
       },
     ]);
 
-    // eslint-disable-next-line cypress/no-unnecessary-waiting
     cy.get('[data-cy=editorjs]')
       .get('div.ce-block')
       .click()
@@ -483,7 +483,6 @@ describe('onChange callback', () => {
       .get('div.ce-block')
       .click();
 
-    // eslint-disable-next-line cypress/no-unnecessary-waiting, @typescript-eslint/no-magic-numbers
     cy.wait(500).then(() => {
       cy.get('@onChange').should('have.callCount', 0);
     });
@@ -562,7 +561,6 @@ describe('onChange callback', () => {
     /**
      * Emulate tool's internal attribute mutation
      */
-    // eslint-disable-next-line cypress/no-unnecessary-waiting, @typescript-eslint/no-magic-numbers
     cy.wait(100).then(() => {
       toolWrapper.setAttribute('some-changed-attr', 'some-new-value');
     });
@@ -570,9 +568,86 @@ describe('onChange callback', () => {
     /**
      * Check that onChange callback was not called
      */
-    // eslint-disable-next-line cypress/no-unnecessary-waiting, @typescript-eslint/no-magic-numbers
     cy.wait(500).then(() => {
       cy.get('@onChange').should('have.callCount', 0);
     });
   });
+
+  it('should be called on blocks.clear() with removed and added blocks', () => {
+    createEditor([
+      {
+        type: 'paragraph',
+        data: {
+          text: 'The first paragraph',
+        },
+      },
+      {
+        type: 'paragraph',
+        data: {
+          text: 'The second paragraph',
+        },
+      },
+    ]);
+
+    cy.get<EditorJS>('@editorInstance')
+      .then(async editor => {
+        cy.wrap(editor.blocks.clear());
+      });
+
+    cy.get('@onChange').should(($callback) => {
+      return beCalledWithBatchedEvents($callback, [
+        {
+          type: BlockRemovedMutationType,
+        },
+        {
+          type: BlockRemovedMutationType,
+        },
+        {
+          type: BlockAddedMutationType,
+        },
+      ]);
+    });
+  });
+
+  it('should be called on blocks.render() on non-empty editor with removed blocks', () => {
+    createEditor([
+      {
+        type: 'paragraph',
+        data: {
+          text: 'The first paragraph',
+        },
+      },
+      {
+        type: 'paragraph',
+        data: {
+          text: 'The second paragraph',
+        },
+      },
+    ]);
+
+    cy.get<EditorJS>('@editorInstance')
+      .then(async editor => {
+        cy.wrap(editor.blocks.render({
+          blocks: [
+            {
+              type: 'paragraph',
+              data: {
+                text: 'The new paragraph',
+              },
+            },
+          ],
+        }));
+      });
+
+    cy.get('@onChange').should(($callback) => {
+      return beCalledWithBatchedEvents($callback, [
+        {
+          type: BlockRemovedMutationType,
+        },
+        {
+          type: BlockRemovedMutationType,
+        },
+      ]);
+    });
+  });
 });
diff --git a/test/cypress/tests/sanitisation.cy.ts b/test/cypress/tests/sanitisation.cy.ts
index b515ccc7..62610444 100644
--- a/test/cypress/tests/sanitisation.cy.ts
+++ b/test/cypress/tests/sanitisation.cy.ts
@@ -1,15 +1,9 @@
+import type EditorJS from '../../../types/index';
+import { OutputData } from '../../../types/index';
+
+
 /* eslint-disable @typescript-eslint/no-explicit-any */
 describe('Output sanitization', () => {
-  beforeEach(function () {
-    cy.createEditor({}).as('editorInstance');
-  });
-
-  afterEach(function () {
-    if (this.editorInstance) {
-      this.editorInstance.destroy();
-    }
-  });
-
   context('Output should save inline formatting', () => {
     it('should save initial formatting for paragraph', () => {
       cy.createEditor({
@@ -19,16 +13,21 @@ describe('Output sanitization', () => {
             data: { text: '<b>Bold text</b>' },
           } ],
         },
-      }).then(async editor => {
-        const output = await (editor as any).save();
+      })
+        .then(async editor => {
+          cy.wrap<OutputData>(await editor.save())
+            .then((output) => {
+              const boldText = output.blocks[0].data.text;
 
-        const boldText = output.blocks[0].data.text;
-
-        expect(boldText).to.eq('<b>Bold text</b>');
-      });
+              expect(boldText).to.eq('<b>Bold text</b>');
+            });
+        });
     });
 
     it('should save formatting for paragraph', () => {
+      cy.createEditor({})
+        .as('editorInstance');
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .click()
@@ -42,16 +41,21 @@ describe('Output sanitization', () => {
         .get('div.ce-block')
         .click();
 
-      cy.get('@editorInstance').then(async editorInstance => {
-        const output = await (editorInstance as any).save();
+      cy.get<EditorJS>('@editorInstance')
+        .then(async editorInstance => {
+          cy.wrap(await editorInstance.save())
+            .then((output) => {
+              const text = output.blocks[0].data.text;
 
-        const text = output.blocks[0].data.text;
-
-        expect(text).to.match(/<b>This text should be bold\.(<br>)?<\/b>/);
-      });
+              expect(text).to.match(/<b>This text should be bold\.(<br>)?<\/b>/);
+            });
+        });
     });
 
     it('should save formatting for paragraph on paste', () => {
+      cy.createEditor({})
+        .as('editorInstance');
+
       cy.get('[data-cy=editorjs]')
         .get('div.ce-block')
         .paste({
@@ -59,13 +63,15 @@ describe('Output sanitization', () => {
           'text/html': '<p>Text</p><p><b>Bold text</b></p>',
         });
 
-      cy.get('@editorInstance').then(async editorInstance => {
-        const output = await (editorInstance as any).save();
+      cy.get<EditorJS>('@editorInstance')
+        .then(async editorInstance => {
+          cy.wrap<OutputData>(await editorInstance.save())
+            .then((output) => {
+              const boldText = output.blocks[1].data.text;
 
-        const boldText = output.blocks[1].data.text;
-
-        expect(boldText).to.eq('<b>Bold text</b>');
-      });
+              expect(boldText).to.eq('<b>Bold text</b>');
+            });
+        });
     });
   });
 });
diff --git a/test/cypress/tests/utils/flipper.cy.ts b/test/cypress/tests/utils/flipper.cy.ts
index 5a682610..59b5908a 100644
--- a/test/cypress/tests/utils/flipper.cy.ts
+++ b/test/cypress/tests/utils/flipper.cy.ts
@@ -37,20 +37,6 @@ class SomePlugin {
 }
 
 describe('Flipper', () => {
-  beforeEach(function () {
-    cy.createEditor({
-      tools: {
-        sometool: SomePlugin,
-      },
-    }).as('editorInstance');
-  });
-
-  afterEach(function () {
-    if (this.editorInstance) {
-      this.editorInstance.destroy();
-    }
-  });
-
   it('should prevent plugins event handlers from being called while keyboard navigation', () => {
     const TAB_KEY_CODE = 9;
     const ARROW_DOWN_KEY_CODE = 40;
@@ -58,15 +44,23 @@ describe('Flipper', () => {
 
     const sampleText = 'sample text';
 
+    cy.createEditor({
+      tools: {
+        sometool: SomePlugin,
+      },
+      data: {
+        blocks: [
+          {
+            type: 'sometool',
+            data: {
+            },
+          },
+        ],
+      },
+    });
+
     cy.spy(SomePlugin, 'pluginInternalKeydownHandler');
 
-    // Insert sometool block and enter sample text
-    cy.get('[data-cy=editorjs]')
-      .get('div.ce-block')
-      .trigger('keydown', { keyCode: TAB_KEY_CODE });
-
-    cy.get('[data-item-name=sometool]').click();
-
     cy.get('[data-cy=editorjs]')
       .get('.cdx-some-plugin')
       .focus()
diff --git a/types/api/blocks.d.ts b/types/api/blocks.d.ts
index b1aabcd5..8f9f15ee 100644
--- a/types/api/blocks.d.ts
+++ b/types/api/blocks.d.ts
@@ -1,4 +1,4 @@
-import {OutputData} from '../data-formats/output-data';
+import {OutputBlockData, OutputData} from '../data-formats/output-data';
 import {BlockToolData, ToolConfig} from '../tools';
 import {BlockAPI} from './block';
 
@@ -103,7 +103,6 @@ export interface Blocks {
    * @param {boolean?} needToFocus - flag to focus inserted Block
    * @param {boolean?} replace - should the existed Block on that index be replaced or not
    * @param {string} id — An optional id for the new block. If omitted then the new id will be generated
-
    */
   insert(
     type?: string,
@@ -115,6 +114,14 @@ export interface Blocks {
     id?: string,
   ): BlockAPI;
 
+  /**
+   * Inserts several Blocks to specified index
+   */
+  insertMany(
+    blocks: OutputBlockData[],
+    index?: number,
+  ): BlockAPI[];
+
 
   /**
    * Creates data of an empty block with a passed type.
diff --git a/vite.config.js b/vite.config.js
index b3464291..63c4ca9d 100644
--- a/vite.config.js
+++ b/vite.config.js
@@ -65,4 +65,4 @@ export default {
   plugins: [
     cssInjectedByJsPlugin(),
   ],
-};
\ No newline at end of file
+};
diff --git a/yarn.lock b/yarn.lock
index 10e21828..6c53942c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -571,10 +571,10 @@
   dependencies:
     "@codexteam/icons" "^0.0.5"
 
-"@editorjs/paragraph@^2.9.0":
-  version "2.9.0"
-  resolved "https://registry.yarnpkg.com/@editorjs/paragraph/-/paragraph-2.9.0.tgz#22f508b3771a4f98650e8bb37d628e230f0a378c"
-  integrity sha512-lI6x1eiqFx2X3KmMak6gBlimFqXhG35fQpXMxzrjIphNLr4uPsXhVbyMPimPoLUnS9rM6Q00vptXmP2QNDd0zg==
+"@editorjs/paragraph@^2.10.0":
+  version "2.10.0"
+  resolved "https://registry.yarnpkg.com/@editorjs/paragraph/-/paragraph-2.10.0.tgz#dcf152e69738a9399b4af83262606d76cf1376e5"
+  integrity sha512-AzaGxR9DQAdWhx43yupBcwqtwH0WWi5jBDOCSeALIK86IYOnO6Lp4anEbH8IYmYrE/5MdnRiTwdU8/Xs8W15Nw==
   dependencies:
     "@codexteam/icons" "^0.0.4"
 
@@ -1649,6 +1649,17 @@ cypress-intellij-reporter@^0.0.7:
   dependencies:
     mocha latest
 
+cypress-terminal-report@^5.3.2:
+  version "5.3.2"
+  resolved "https://registry.yarnpkg.com/cypress-terminal-report/-/cypress-terminal-report-5.3.2.tgz#3a6b1cbda6101498243d17c5a2a646cb69af0336"
+  integrity sha512-0Gf/pXjrYpTkf2aR3LAFGoxEM0KulWsMKCu+52YJB6l7GEP2RLAOAr32tcZHZiL2EWnS0vE4ollomMzGvCci0w==
+  dependencies:
+    chalk "^4.0.0"
+    fs-extra "^10.1.0"
+    safe-json-stringify "^1.2.0"
+    semver "^7.3.5"
+    tv4 "^1.3.0"
+
 cypress@^12.9.0:
   version "12.9.0"
   resolved "https://registry.yarnpkg.com/cypress/-/cypress-12.9.0.tgz#e6ab43cf329fd7c821ef7645517649d72ccf0a12"
@@ -4443,6 +4454,11 @@ safe-buffer@^5.1.0:
   version "5.2.0"
   resolved "https://registry.yarnpkg.com/safe-buffer/-/safe-buffer-5.2.0.tgz#b74daec49b1148f88c64b68d49b1e815c1f2f519"
 
+safe-json-stringify@^1.2.0:
+  version "1.2.0"
+  resolved "https://registry.yarnpkg.com/safe-json-stringify/-/safe-json-stringify-1.2.0.tgz#356e44bc98f1f93ce45df14bcd7c01cda86e0afd"
+  integrity sha512-gH8eh2nZudPQO6TytOvbxnuhYBOvDBBLW52tz5q6X58lJcd/tkmqFR+5Z9adS8aJtURSXWThWy/xJtJwixErvg==
+
 safe-regex-test@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/safe-regex-test/-/safe-regex-test-1.0.0.tgz#793b874d524eb3640d1873aad03596db2d4f2295"
@@ -4474,6 +4490,13 @@ semver@^7.0.0, semver@^7.3.2, semver@^7.3.4, semver@^7.3.7, semver@^7.3.8:
   dependencies:
     lru-cache "^6.0.0"
 
+semver@^7.3.5:
+  version "7.5.4"
+  resolved "https://registry.yarnpkg.com/semver/-/semver-7.5.4.tgz#483986ec4ed38e1c6c48c34894a9182dbff68a6e"
+  integrity sha512-1bCSESV6Pv+i21Hvpxp3Dx+pSD8lIPt8uVjRrxAUt/nbswYc+tK6Y2btiULjd4+fnq15PX+nqQDC7Oft7WkwcA==
+  dependencies:
+    lru-cache "^6.0.0"
+
 serialize-javascript@6.0.0:
   version "6.0.0"
   resolved "https://registry.yarnpkg.com/serialize-javascript/-/serialize-javascript-6.0.0.tgz#efae5d88f45d7924141da8b5c3a7a7e663fefeb8"
@@ -4936,6 +4959,11 @@ tunnel-agent@^0.6.0:
   dependencies:
     safe-buffer "^5.0.1"
 
+tv4@^1.3.0:
+  version "1.3.0"
+  resolved "https://registry.yarnpkg.com/tv4/-/tv4-1.3.0.tgz#d020c846fadd50c855abb25ebaecc68fc10f7963"
+  integrity sha512-afizzfpJgvPr+eDkREK4MxJ/+r8nEEHcmitwgnPUqpaP+FpwQyadnxNoSACbgc/b1LsZYtODGoPiFxQrgJgjvw==
+
 tweetnacl@^0.14.3, tweetnacl@~0.14.0:
   version "0.14.5"
   resolved "https://registry.yarnpkg.com/tweetnacl/-/tweetnacl-0.14.5.tgz#5ae68177f192d4456269d108afa93ff8743f4f64"