diff --git a/extensions/html-language-features/server/src/test/embedded.test.ts b/extensions/html-language-features/server/src/test/embedded.test.ts
new file mode 100644
index 0000000000000..f28a12d940654
--- /dev/null
+++ b/extensions/html-language-features/server/src/test/embedded.test.ts
@@ -0,0 +1,144 @@
+/*---------------------------------------------------------------------------------------------
+ * Copyright (c) Microsoft Corporation. All rights reserved.
+ * Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+import 'mocha';
+import * as assert from 'assert';
+import * as embeddedSupport from '../modes/embeddedSupport';
+import { forEachEmbeddedCode, SourceMap, VirtualCode } from '@volar/language-core';
+import { htmlLanguagePlugin } from '../modes/languagePlugin';
+import { getLanguageService } from 'vscode-html-languageservice';
+
+suite('HTML Embedded Support', () => {
+
+ const htmlLanguageService = getLanguageService();
+
+ function assertLanguageId(value: string, expectedLanguageId: string | undefined): void {
+ const offset = value.indexOf('|');
+ value = value.substr(0, offset) + value.substr(offset + 1);
+
+ const virtualCode = htmlLanguagePlugin.createVirtualCode('', 'html', {
+ getText: () => value,
+ getLength: () => value.length,
+ getChangeRange: () => undefined,
+ });
+ assert(!!virtualCode);
+
+ let mappedCode: VirtualCode | undefined;
+
+ for (const embeddedCode of [...forEachEmbeddedCode(virtualCode)].reverse()) {
+ const map = new SourceMap(embeddedCode.mappings);
+ const mapped = map.getGeneratedOffset(offset);
+ if (mapped) {
+ mappedCode = embeddedCode;
+ break;
+ }
+ }
+
+ assert(!!mappedCode);
+ assert.strictEqual(mappedCode.languageId, expectedLanguageId);
+ }
+
+ function assertEmbeddedLanguageContent(value: string, languageId: string, expectedContents: string[]): void {
+ const docRegions = embeddedSupport.getDocumentRegions(htmlLanguageService, value);
+ const contents = docRegions.getEmbeddedRegions().filter(r => r.languageId === languageId);
+ assert.strictEqual(contents.length, expectedContents.length);
+ for (let i = 0; i < contents.length; i++) {
+ assert.strictEqual(contents[i].content, expectedContents[i]);
+ }
+ }
+
+ test('Styles', function (): any {
+ assertLanguageId('|', 'html');
+ assertLanguageId('