add clearPage test utility function

npm/ng-packs/packages/core/testing/src/lib/utils/clear-page.util.ts

@@ -0,0 +1,10 @@
+import { ComponentFixture } from '@angular/core/testing';
+
+export function clearPage<T extends any>(_fixture: ComponentFixture<T>) {
+  if (!document) return;
+
+  const elements = document.querySelectorAll('body > *');
+  elements.forEach(element => {
+    if (/^(abp|ngb)-/i.test(element.tagName)) document.body.removeChild(element);
+  });
+}

npm/ng-packs/packages/core/testing/src/lib/utils/index.ts

@@ -0,0 +1 @@
+export * from './clear-page.util';

npm/ng-packs/packages/core/testing/src/public-api.ts

@@ -1,2 +1,3 @@
 export * from './lib/core-testing.module';
 export * from './lib/services';
+export * from './lib/utils';