feat(test): add challenge 18 and 19 avout testing

apps/testing-nested/src/app/child.component.spec.ts

@@ -0,0 +1,12 @@
+import { render } from '@testing-library/angular';
+import { ChildComponent } from './child.component';
+
+describe('ChildComponent', () => {
+  test('add Good title and send request title with no error', async () => {
+    await render(ChildComponent);
+  });
+
+  test('fail validating title because no title were typed', async () => {
+    await render(ChildComponent);
+  });
+});