feat(forms): add tests for markAllAsTouched()

Add tests to validate the behavior

packages/forms/test/form_group_spec.ts

@@ -86,6 +86,56 @@ import {of } from 'rxjs';
 
     });
 
+    describe('markAllAsTouched', () => {
+      it('should mark all descendants as touched', () => {
+        const formGroup: FormGroup = new FormGroup({
+          'c1': new FormControl('v1'),
+          'group': new FormGroup({'c2': new FormControl('v2'), 'c3': new FormControl('v3')}),
+          'array': new FormArray([new FormControl('v4'), new FormControl('v5'), new FormGroup({'c4': new FormControl('v4')})])
+        });
+
+        formGroup.markAllAsTouched();
+
+        expect(formGroup.touched).toBe(true);
+
+        const control1 = formGroup.get('c1') as FormControl;
+
+        expect(control1.touched).toBe(true);
+
+        const innerGroup = formGroup.get('group') as FormGroup;
+
+        expect(innerGroup.touched).toBe(true);
+
+        const innerGroupFirstChildCtrl = innerGroup.get('c2') as FormControl;
+
+        expect(innerGroupFirstChildCtrl.touched).toBe(true);
+
+        const innerGroupSecondChildCtrl = innerGroup.get('c3') as FormControl;
+
+        expect(innerGroupSecondChildCtrl.touched).toBe(true);
+
+        const array = formGroup.get('array') as FormArray;
+
+        expect(array.touched).toBe(true);
+
+        const arrayFirstChildCtrl = array.controls[0] as FormControl;
+
+        expect(arrayFirstChildCtrl.touched).toBe(true);
+
+        const arraySecondChildCtrl = array.controls[1] as FormControl;
+
+        expect(arraySecondChildCtrl.touched).toBe(true);
+
+        const arrayFirstChildGroup = array.controls[2] as FormGroup;
+
+        expect(arrayFirstChildGroup.touched).toBe(true);
+
+        const arrayFirstChildGroupFirstChildCtrl = arrayFirstChildGroup.get('c4') as FormControl;
+
+        expect(arrayFirstChildGroupFirstChildCtrl.touched).toBe(true);
+      })
+    });
+
     describe('adding and removing controls', () => {
       it('should update value and validity when control is added', () => {
         const g = new FormGroup({'one': new FormControl('1')});