test: add more unit tests

app/command/bad-practice-editor.spec.ts

@@ -15,4 +15,18 @@ describe('BadPracticeEditor', () => {
     editor.undo();
     expect(editor.getContent()).toBe("Hello World");
   })
+
+  it('should do nothing if there is nothing to undo', () => {
+    const editor = new TextEditor();
+    editor.setContent("Hello World");
+    editor.undo();
+    expect(editor.getContent()).toBe("Hello World");
+  })
+
+  it('should make the text italic', () => {
+    const editor = new TextEditor();
+    editor.setContent("Hello World");
+    editor.italic(6, 5);
+    // add implementation here
+  })
 });

app/command/bad-practice-editor.ts

@@ -21,7 +21,7 @@ export class TextEditor {
     this.content = this.content.slice(0, start) + boldedText + this.content.slice(start + length);
   }
 
-  public italic() { /* ... */ }
+  public italic(start: number, length: number) { /* ... */ }
 
   // Undo the last operation (revert to the previous state)
   public undo(): void {

app/command/command-manager.spec.ts

@@ -4,9 +4,13 @@ import { ICommand } from "./interface";
 describe('Command Manager', () => {
   const writeCommand: ICommand = {
     execute: jest.fn(),
-    undo: jest.fn()
+    undo: jest.fn(),
   };
 
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
   it('should execute command', () => {
     const commandManager = new CommandManager();
     commandManager.execute(writeCommand);
@@ -20,4 +24,14 @@ describe('Command Manager', () => {
     expect(writeCommand.execute).toHaveBeenCalled();
     expect(writeCommand.undo).toHaveBeenCalled();
   })
+
+  it('should redo command', () => {
+    const commandManager = new CommandManager();
+    commandManager.execute(writeCommand);
+    commandManager.undo();
+    commandManager.redo();
+    expect(writeCommand.execute).toHaveBeenCalledTimes(2);
+    expect(writeCommand.undo).toHaveBeenCalled();
+
+  })
 });