deprecate writeSync

src/browser/TestUtils.test.ts

@@ -21,6 +21,9 @@ export class TestTerminal extends Terminal {
   public get curAttrData(): IAttributeData { return (this as any)._inputHandler._curAttrData; }
   public keyDown(ev: any): boolean | undefined { return this._keyDown(ev); }
   public keyPress(ev: any): boolean { return this._keyPress(ev); }
+  public writeP(data: string | Uint8Array): Promise<void> {
+    return new Promise(r => this.write(data, r));
+  }
 }
 
 export class MockTerminal implements ITerminal {