Expose API method for writing to application side (#4948)

src/browser/TestUtils.test.ts

@@ -72,6 +72,9 @@ export class MockTerminal implements ITerminal {
   public focus(): void {
     throw new Error('Method not implemented.');
   }
+  public input(data: string): void {
+    throw new Error('Method not implemented.');
+  }
   public resize(columns: number, rows: number): void {
     throw new Error('Method not implemented.');
   }