From 2cb3d174ffdfff72054271450f1030f6f3969e06 Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Mon, 12 Oct 2026 11:06:33 +0000
Subject: [PATCH] fix(@angular/build): disable Vitest fsModuleCache in
 unit-test builder

Vitest 5.0.4 enabled `fsModuleCache` by default, which caches transformed
modules on disk keyed by the raw source file content on disk before calling
Vite's `load()` hook. Because `@angular/build:unit-test` pre-bundles test entry
points and their imported application modules into memory, changes to imported
application files do not change the on-disk `.spec.ts` file content, causing
Vitest's `fsModuleCache` to serve stale cached bundles across test runs.
---
 .../build/src/builders/unit-test/runners/vitest/plugins.ts      | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts b/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
index 6be4c6e8ebe3..ec0cd0a8f269 100644
--- a/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
+++ b/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
@@ -271,6 +271,7 @@ export async function createVitestConfigPlugin(
         test: {
           name: projectName,
           include,
+          fsModuleCache: false,
           // CLI provider browser options override, if present
           ...(browser ? { browser } : {}),
           // Only override if the user explicitly set it via CLI
@@ -290,6 +291,7 @@ export async function createVitestConfigPlugin(
 
       return {
         test: {
+          fsModuleCache: false,
           coverage: await generateCoverageOption(
             options.coverage,
             testConfig?.coverage,