From 134f58e466c9b8451428d4614e264fc340a423f0 Mon Sep 17 00:00:00 2001
From: Karan Mistry <karan.mistry@siemens.com>
Date: Sat, 10 Jan 2026 16:25:52 +0530
Subject: [PATCH] build: add 'update' option for Vitest runner and
 corresponding tests

Fixes #32218
---
 .../build/src/builders/unit-test/options.ts   |  7 +-
 .../unit-test/runners/vitest/executor.ts      |  1 +
 .../build/src/builders/unit-test/schema.json  |  5 ++
 .../unit-test/tests/options/update_spec.ts    | 74 +++++++++++++++++++
 4 files changed, 86 insertions(+), 1 deletion(-)
 create mode 100644 packages/angular/build/src/builders/unit-test/tests/options/update_spec.ts

diff --git a/packages/angular/build/src/builders/unit-test/options.ts b/packages/angular/build/src/builders/unit-test/options.ts
index 7f8f8db182fe..8f711c2a7a6a 100644
--- a/packages/angular/build/src/builders/unit-test/options.ts
+++ b/packages/angular/build/src/builders/unit-test/options.ts
@@ -54,12 +54,16 @@ export async function normalizeOptions(
   const buildTargetSpecifier = options.buildTarget ?? `::development`;
   const buildTarget = targetFromTargetString(buildTargetSpecifier, projectName, 'build');
 
-  const { runner, browsers, progress, filter, browserViewport, ui, runnerConfig } = options;
+  const { runner, browsers, progress, filter, browserViewport, ui, runnerConfig, update } = options;
 
   if (ui && runner !== Runner.Vitest) {
     throw new Error('The "ui" option is only available for the "vitest" runner.');
   }
 
+  if (update && runner !== Runner.Vitest) {
+    throw new Error('The "update" option is only available for the "vitest" runner.');
+  }
+
   const [width, height] = browserViewport?.split('x').map(Number) ?? [];
 
   let tsConfig = options.tsConfig;
@@ -132,6 +136,7 @@ export async function normalizeOptions(
           ? true
           : path.resolve(workspaceRoot, runnerConfig)
         : runnerConfig,
+    update: update ?? false,
   };
 }
 
diff --git a/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts b/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts
index ed754d9f9c30..5bbcd3b6f431 100644
--- a/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts
+++ b/packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts
@@ -238,6 +238,7 @@ export class VitestExecutor implements TestExecutor {
         watch,
         ...(typeof ui === 'boolean' ? { ui } : {}),
         ...debugOptions,
+        update: this.options.update,
       },
       {
         // Note `.vitest` is auto appended to the path.
diff --git a/packages/angular/build/src/builders/unit-test/schema.json b/packages/angular/build/src/builders/unit-test/schema.json
index 2a3cf27719e8..c1118738ffc3 100644
--- a/packages/angular/build/src/builders/unit-test/schema.json
+++ b/packages/angular/build/src/builders/unit-test/schema.json
@@ -269,6 +269,11 @@
       "description": "Dumps build output files to the `.angular/cache` directory for debugging purposes.",
       "default": false,
       "visible": false
+    },
+    "update": {
+      "type": "boolean",
+      "description": "Updates test snapshots to match the current test output. This option is only available for the Vitest runner.",
+      "default": false
     }
   },
   "additionalProperties": false,
diff --git a/packages/angular/build/src/builders/unit-test/tests/options/update_spec.ts b/packages/angular/build/src/builders/unit-test/tests/options/update_spec.ts
new file mode 100644
index 000000000000..710f59cd8f89
--- /dev/null
+++ b/packages/angular/build/src/builders/unit-test/tests/options/update_spec.ts
@@ -0,0 +1,74 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+
+import { execute } from '../../index';
+import {
+  BASE_OPTIONS,
+  describeBuilder,
+  UNIT_TEST_BUILDER_INFO,
+  setupApplicationTarget,
+} from '../setup';
+
+describeBuilder(execute, UNIT_TEST_BUILDER_INFO, (harness) => {
+  describe('Option: "update"', () => {
+    beforeEach(() => {
+      setupApplicationTarget(harness);
+    });
+
+    describe('Vitest Runner', () => {
+      it('should work with update flag enabled', async () => {
+        harness.useTarget('test', {
+          ...BASE_OPTIONS,
+          update: true,
+        });
+
+        const { result } = await harness.executeOnce();
+
+        expect(result?.success).toBeTrue();
+      });
+
+      it('should work with update flag disabled', async () => {
+        harness.useTarget('test', {
+          ...BASE_OPTIONS,
+          update: false,
+        });
+
+        const { result } = await harness.executeOnce();
+
+        expect(result?.success).toBeTrue();
+      });
+
+      it('should work without update flag (default)', async () => {
+        harness.useTarget('test', {
+          ...BASE_OPTIONS,
+        });
+
+        const { result } = await harness.executeOnce();
+
+        expect(result?.success).toBeTrue();
+      });
+    });
+
+    describe('Karma Runner', () => {
+      it('should throw an error when update is used with karma', async () => {
+        harness.useTarget('test', {
+          ...BASE_OPTIONS,
+          runner: 'karma',
+          update: true,
+        });
+
+        const { result, error } = await harness.executeOnce({ outputLogsOnException: false });
+
+        expect(result).toBeUndefined();
+        expect(error?.message).toContain(
+          'The "update" option is only available for the "vitest" runner.',
+        );
+      });
+    });
+  });
+});