fix

src/app/shared/chat/add-user.pipe.spec.ts

@@ -0,0 +1,8 @@
+import { AddUserPipe } from './add-user.pipe';
+
+describe('AddUserPipe', () => {
+  it('create an instance', () => {
+    const pipe = new AddUserPipe();
+    expect(pipe).toBeTruthy();
+  });
+});

src/app/shared/chat/add-user.pipe.ts

@@ -0,0 +1,12 @@
+import { Pipe, PipeTransform } from '@angular/core';
+
+@Pipe({
+  name: 'addUser'
+})
+export class AddUserPipe implements PipeTransform {
+
+  transform(value: unknown, ...args: unknown[]): unknown {
+    return null;
+  }
+
+}