From 16c8ee211b539257801415efa7dbe7d51fe4ef6c Mon Sep 17 00:00:00 2001
From: Teo <teo.eterovic@gmail.com>
Date: Wed, 9 Jul 2025 20:34:55 +0200
Subject: [PATCH] feat(@angular/build): add headless mode for vitest browser
 mode

---
 .../angular/build/src/builders/unit-test/builder.ts | 13 ++++++++++++-
 .../build/src/builders/unit-test/schema.json        |  2 +-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/packages/angular/build/src/builders/unit-test/builder.ts b/packages/angular/build/src/builders/unit-test/builder.ts
index fd9f88580d70..5bf1556cadcb 100644
--- a/packages/angular/build/src/builders/unit-test/builder.ts
+++ b/packages/angular/build/src/builders/unit-test/builder.ts
@@ -331,6 +331,15 @@ function findBrowserProvider(
   }
 }
 
+function normalizeBrowserName(browserName: string): string {
+  // Normalize browser names to match Vitest's expectations for headless but also supports karma's names
+  // e.g., 'ChromeHeadless' -> 'chrome', 'FirefoxHeadless'
+  // and 'Chrome' -> 'chrome', 'Firefox' -> 'firefox'.
+  const normalized = browserName.toLowerCase();
+
+  return normalized.replace(/headless$/, '');
+}
+
 function setupBrowserConfiguration(
   browsers: string[] | undefined,
   debug: boolean,
@@ -378,8 +387,10 @@ function setupBrowserConfiguration(
   const browser = {
     enabled: true,
     provider,
+    headless: browsers.some((name) => name.toLowerCase().includes('headless')),
+
     instances: browsers.map((browserName) => ({
-      browser: browserName,
+      browser: normalizeBrowserName(browserName),
     })),
   };
 
diff --git a/packages/angular/build/src/builders/unit-test/schema.json b/packages/angular/build/src/builders/unit-test/schema.json
index 0f54d813ace1..8628bb9725e9 100644
--- a/packages/angular/build/src/builders/unit-test/schema.json
+++ b/packages/angular/build/src/builders/unit-test/schema.json
@@ -19,7 +19,7 @@
       "enum": ["karma", "vitest"]
     },
     "browsers": {
-      "description": "A list of browsers to use for test execution. If undefined, jsdom on Node.js will be used instead of a browser.",
+      "description": "A list of browsers to use for test execution. If undefined, jsdom on Node.js will be used instead of a browser. For Vitest and Karma, browser names ending with 'Headless' (e.g., 'ChromeHeadless') will enable headless mode for that browser.",
       "type": "array",
       "items": {
         "type": "string"