diff --git a/packages/angular/build/src/builders/unit-test/builder.ts b/packages/angular/build/src/builders/unit-test/builder.ts
index 122039595bd9..6f2edd0281d7 100644
--- a/packages/angular/build/src/builders/unit-test/builder.ts
+++ b/packages/angular/build/src/builders/unit-test/builder.ts
@@ -12,7 +12,7 @@ import {
   targetStringFromTarget,
 } from '@angular-devkit/architect';
 import assert from 'node:assert';
-import { rm } from 'node:fs/promises';
+import { readFile, rm } from 'node:fs/promises';
 import path from 'node:path';
 import { createVirtualModulePlugin } from '../../tools/esbuild/virtual-module-plugin';
 import { assertIsError } from '../../utils/error';
@@ -244,22 +244,34 @@ export async function* execute(
   let buildTargetOptions: ApplicationBuilderInternalOptions;
   try {
     const builderName = await context.getBuilderNameForTarget(normalizedOptions.buildTarget);
-    if (
-      builderName !== '@angular/build:application' &&
-      // TODO: Add comprehensive support for ng-packagr.
-      builderName !== '@angular/build:ng-packagr'
-    ) {
+    if (builderName === '@angular/build:application') {
+      buildTargetOptions = (await context.validateOptions(
+        await context.getTargetOptions(normalizedOptions.buildTarget),
+        builderName,
+      )) as unknown as ApplicationBuilderInternalOptions;
+    } else if (builderName === '@angular/build:ng-packagr') {
+      const ngPackagrOptions = await context.validateOptions(
+        await context.getTargetOptions(normalizedOptions.buildTarget),
+        builderName,
+      );
+
+      buildTargetOptions = await transformNgPackagrOptions(
+        context,
+        ngPackagrOptions,
+        normalizedOptions.projectRoot,
+      );
+    } else {
       context.logger.warn(
         `The 'buildTarget' is configured to use '${builderName}', which is not supported. ` +
-          `The 'unit-test' builder is designed to work with '@angular/build:application'. ` +
+          `The 'unit-test' builder is designed to work with '@angular/build:application' or '@angular/build:ng-packagr'. ` +
           'Unexpected behavior or build failures may occur.',
       );
-    }
 
-    buildTargetOptions = (await context.validateOptions(
-      await context.getTargetOptions(normalizedOptions.buildTarget),
-      builderName,
-    )) as unknown as ApplicationBuilderInternalOptions;
+      buildTargetOptions = (await context.validateOptions(
+        await context.getTargetOptions(normalizedOptions.buildTarget),
+        builderName,
+      )) as unknown as ApplicationBuilderInternalOptions;
+    }
   } catch (e) {
     assertIsError(e);
     context.logger.error(
@@ -335,3 +347,42 @@ export async function* execute(
     yield { success: false };
   }
 }
+
+async function transformNgPackagrOptions(
+  context: BuilderContext,
+  options: Record<string, unknown>,
+  projectRoot: string,
+): Promise<ApplicationBuilderInternalOptions> {
+  const projectPath = options['project'];
+
+  let ngPackagePath: string;
+  if (projectPath) {
+    if (typeof projectPath !== 'string') {
+      throw new Error('ng-packagr builder options "project" property must be a string.');
+    }
+    ngPackagePath = path.join(context.workspaceRoot, projectPath);
+  } else {
+    ngPackagePath = path.join(projectRoot, 'ng-package.json');
+  }
+
+  let ngPackageJson;
+  try {
+    ngPackageJson = JSON.parse(await readFile(ngPackagePath, 'utf-8'));
+  } catch (e) {
+    assertIsError(e);
+    throw new Error(`Could not read ng-package.json at ${ngPackagePath}: ${e.message}`);
+  }
+
+  const lib = ngPackageJson['lib'] || {};
+  const styleIncludePaths = lib['styleIncludePaths'] || [];
+  const assets = ngPackageJson['assets'] || [];
+  const inlineStyleLanguage = ngPackageJson['inlineStyleLanguage'];
+
+  return {
+    stylePreprocessorOptions: styleIncludePaths.length
+      ? { includePaths: styleIncludePaths }
+      : undefined,
+    assets: assets.length ? assets : undefined,
+    inlineStyleLanguage: typeof inlineStyleLanguage === 'string' ? inlineStyleLanguage : undefined,
+  } as ApplicationBuilderInternalOptions;
+}
diff --git a/tests/e2e/tests/vitest/library.ts b/tests/e2e/tests/vitest/library.ts
new file mode 100644
index 000000000000..ba1e31dc38f8
--- /dev/null
+++ b/tests/e2e/tests/vitest/library.ts
@@ -0,0 +1,50 @@
+import assert from 'node:assert/strict';
+import { updateJsonFile } from '../../utils/project';
+import { ng, silentNpm } from '../../utils/process';
+import { createDir, writeFile } from '../../utils/fs';
+
+export default async function (): Promise<void> {
+  // Install Vitest deps
+  await silentNpm('install', 'vitest@^4.0.8', 'jsdom@^27.1.0', '--save-dev');
+
+  // Generate a library
+  await ng('generate', 'library', 'my-lib', '--test-runner', 'vitest');
+
+  // Setup Style Include Paths test
+  // 1. Create a shared SCSS file
+  await createDir('projects/my-lib/src/styles');
+  await writeFile('projects/my-lib/src/styles/_vars.scss', '$primary-color: red;');
+
+  // 2. Update ng-package.json to include the styles directory
+  await updateJsonFile('projects/my-lib/ng-package.json', (json) => {
+    json['lib'] = {
+      ...json['lib'],
+      styleIncludePaths: ['./src/styles'],
+    };
+  });
+
+  // 3. Update the component to use SCSS and import the shared file
+  // Rename CSS to SCSS
+  await ng(
+    'generate',
+    'component',
+    'styled-comp',
+    '--project=my-lib',
+    '--style=scss',
+    '--skip-import',
+  );
+
+  await writeFile(
+    'projects/my-lib/src/lib/styled-comp/styled-comp.component.scss',
+    `
+      @use 'vars';
+      p { color: vars.$primary-color; }
+    `,
+  );
+
+  // Run the library tests
+  const { stdout } = await ng('test', 'my-lib');
+
+  // Expect tests to pass
+  assert.match(stdout, /passed/, 'Expected library tests to pass.');
+}