diff --git a/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.spec.ts b/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.spec.ts
index 8fd07607db..53888482a3 100644
--- a/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.spec.ts
+++ b/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.spec.ts
@@ -1,13 +1,6 @@
-import { Tree } from '@angular-devkit/schematics';
-import { createEmptyWorkspace } from '@nrwl/workspace/testing';
-import { runMigration } from '../../utils/testing';
-
-function createAngularCLIPoweredWorkspace() {
-  const tree = createEmptyWorkspace(Tree.empty());
-  tree.delete('workspace.json');
-  tree.create('angular.json', '{}');
-  return tree;
-}
+import { readJson, writeJson } from '@nrwl/devkit';
+import { createTreeWithEmptyWorkspace } from '@nrwl/devkit/testing';
+import updateNgccPostinstall from './update-ngcc-postinstall';
 
 describe('Remove ngcc flags from postinstall script', () => {
   [
@@ -33,21 +26,17 @@ describe('Remove ngcc flags from postinstall script', () => {
     },
   ].forEach((testEntry) => {
     it(`should adjust ngcc for: "${testEntry.test}"`, async () => {
-      const tree = createAngularCLIPoweredWorkspace();
+      const tree = createTreeWithEmptyWorkspace(2);
+      tree.delete('workspace.json');
+      tree.write('angular.json', '{}');
+      writeJson(tree, 'package.json', {
+        scripts: { postinstall: testEntry.test },
+      });
 
-      tree.overwrite(
-        '/package.json',
-        JSON.stringify({
-          scripts: {
-            postinstall: testEntry.test,
-          },
-        })
-      );
+      await updateNgccPostinstall(tree);
 
-      const result = await runMigration('update-ngcc-postinstall', {}, tree);
-
-      const packageJson = JSON.parse(result.read('/package.json').toString());
-      expect(packageJson.scripts.postinstall).toEqual(testEntry.expected);
+      const { scripts } = readJson(tree, 'package.json');
+      expect(scripts.postinstall).toEqual(testEntry.expected);
     });
   });
 });
diff --git a/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.ts b/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.ts
index db12abf3fb..8e4d199454 100644
--- a/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.ts
+++ b/packages/angular/src/migrations/update-12-0-0/update-ngcc-postinstall.ts
@@ -1,24 +1,22 @@
-import { chain, SchematicContext, Tree } from '@angular-devkit/schematics';
-import { updateJsonInTree } from '@nrwl/workspace';
-import { formatFiles } from '@nrwl/workspace';
+import type { Tree } from '@nrwl/devkit';
+import { formatFiles, updateJson } from '@nrwl/devkit';
 
-const udpateNgccPostinstallScript = (host: Tree, context: SchematicContext) => {
-  updateJsonInTree('package.json', (json) => {
-    if (
-      json.scripts &&
-      json.scripts.postinstall &&
-      json.scripts.postinstall.includes('ngcc')
-    ) {
-      // if exists, add execution of this script
+export default async function (tree: Tree) {
+  let shouldFormat = false;
+
+  updateJson(tree, 'package.json', (json) => {
+    if (json.scripts?.postinstall?.includes('ngcc')) {
       json.scripts.postinstall = json.scripts.postinstall.replace(
         /(.*)(ngcc --properties es2015 browser module main --first-only --create-ivy-entry-points)(.*)/,
         '$1ngcc --properties es2015 browser module main$3'
       );
+      shouldFormat = true;
     }
-    return json;
-  })(host, context);
-};
 
-export default function () {
-  return chain([udpateNgccPostinstallScript, formatFiles()]);
+    return json;
+  });
+
+  if (shouldFormat) {
+    await formatFiles(tree);
+  }
 }
diff --git a/packages/angular/src/utils/testing.ts b/packages/angular/src/utils/testing.ts
deleted file mode 100644
index d860a190ba..0000000000
--- a/packages/angular/src/utils/testing.ts
+++ /dev/null
@@ -1,47 +0,0 @@
-import { join } from 'path';
-import { SchematicTestRunner } from '@angular-devkit/schematics/testing';
-import { Rule, Tree } from '@angular-devkit/schematics';
-
-const testRunner = new SchematicTestRunner(
-  '@nrwl/angular',
-  join(__dirname, '../../generators.json')
-);
-
-testRunner.registerCollection(
-  '@nrwl/jest',
-  join(__dirname, '../../../jest/generators.json')
-);
-
-testRunner.registerCollection(
-  '@nrwl/workspace',
-  join(__dirname, '../../../workspace/generators.json')
-);
-
-testRunner.registerCollection(
-  '@nrwl/cypress',
-  join(__dirname, '../../../cypress/generators.json')
-);
-
-testRunner.registerCollection(
-  '@nrwl/storybook',
-  join(__dirname, '../../../storybook/generators.json')
-);
-
-const migrationTestRunner = new SchematicTestRunner(
-  '@nrwl/workspace',
-  join(__dirname, '../../migrations.json')
-);
-
-export function runMigration<SchemaOptions extends object = any>(
-  schematicName: string,
-  options: SchemaOptions,
-  tree: Tree
-) {
-  return migrationTestRunner
-    .runSchematicAsync(schematicName, options, tree)
-    .toPromise();
-}
-
-export function callRule(rule: Rule, tree: Tree) {
-  return testRunner.callRule(rule, tree).toPromise();
-}
diff --git a/packages/angular/testing/index.ts b/packages/angular/testing/index.ts
index 078a269351..42b102d44a 100644
--- a/packages/angular/testing/index.ts
+++ b/packages/angular/testing/index.ts
@@ -6,19 +6,19 @@ import {
 } from 'jasmine-marbles';
 
 /**
- * @deprecated Import from 'jasmine-marbles' instead
+ * @deprecated Import from 'jasmine-marbles' instead. Will be removed in Nx v15.
  */
 export const cold = rxjsMarblesCold;
 /**
- * @deprecated Import from 'jasmine-marbles' instead
+ * @deprecated Import from 'jasmine-marbles' instead. Will be removed in Nx v15.
  */
 export const hot = rxjsMarblesHot;
 /**
- * @deprecated Import from 'jasmine-marbles' instead
+ * @deprecated Import from 'jasmine-marbles' instead. Will be removed in Nx v15.
  */
 export const getTestScheduler = rxjsMarblesTestScheduler;
 /**
- * @deprecated Import from 'jasmine-marbles' instead
+ * @deprecated Import from 'jasmine-marbles' instead. Will be removed in Nx v15.
  */
 export const time = rxjsMarblesTime;