diff --git a/packages/frontend/editor-ui/src/plugins/codemirror/typescript/worker/typescript.worker.test.ts b/packages/frontend/editor-ui/src/plugins/codemirror/typescript/worker/typescript.worker.test.ts
index 74fb55d816d..4c36385252c 100644
--- a/packages/frontend/editor-ui/src/plugins/codemirror/typescript/worker/typescript.worker.test.ts
+++ b/packages/frontend/editor-ui/src/plugins/codemirror/typescript/worker/typescript.worker.test.ts
@@ -1,6 +1,12 @@
+import { type ChangeSet, EditorState } from '@codemirror/state';
+import * as tsvfs from '@typescript/vfs';
+import ts from 'typescript';
+import { mock } from 'vitest-mock-extended';
 import type { WorkerInitOptions } from '../types';
 import { worker } from './typescript.worker';
-import { type ChangeSet, EditorState } from '@codemirror/state';
+
+vi.mock('@typescript/vfs');
+vi.mock('typescript');
 
 async function createWorker({
 	doc,
@@ -16,6 +22,14 @@ function myFunction(){
 return $input.all();`;
 	const state = EditorState.create({ doc: doc ?? defaultDoc });
 
+	const mockEnv = mock<tsvfs.VirtualTypeScriptEnvironment>({
+		getSourceFile: vi.fn(() => mock<ts.SourceFile>({ getText: () => state.doc.toString() })),
+		languageService: mock<ts.LanguageService>(),
+	});
+
+	vi.spyOn(tsvfs, 'createDefaultMapFromCDN').mockResolvedValue(new Map());
+	vi.spyOn(tsvfs, 'createVirtualTypeScriptEnvironment').mockResolvedValue(mockEnv);
+
 	const tsWorker = worker.init(
 		{
 			allNodeNames: [],
@@ -32,12 +46,32 @@ return $input.all();`;
 			params: { path: '', type: 'string', value: '' },
 		}),
 	);
-	return await tsWorker;
+	return { tsWorker: await tsWorker, mockEnv };
 }
 
 describe('Typescript Worker', () => {
+	beforeEach(() => {
+		vi.resetAllMocks();
+	});
+
 	it('should return diagnostics', async () => {
-		const tsWorker = await createWorker();
+		const { tsWorker, mockEnv } = await createWorker();
+
+		vi.mocked(mockEnv.languageService.getSemanticDiagnostics).mockReturnValue([
+			mock<ts.Diagnostic>({
+				start: 56,
+				length: 10,
+				code: 6133,
+				messageText: "'myFunction' is declared but its value is never read.",
+			}),
+			mock<ts.Diagnostic>({
+				start: 93,
+				length: 5,
+				code: 6133,
+				messageText: "'myObj' is declared but its value is never read.",
+			}),
+		]);
+		vi.mocked(mockEnv.languageService.getSyntacticDiagnostics).mockReturnValue([]);
 
 		expect(tsWorker.getDiagnostics()).toEqual([
 			{
@@ -55,10 +89,13 @@ describe('Typescript Worker', () => {
 				to: 52,
 			},
 		]);
+
+		expect(mockEnv.languageService.getSemanticDiagnostics).toHaveBeenCalledWith('id.js');
+		expect(mockEnv.languageService.getSyntacticDiagnostics).toHaveBeenCalledWith('id.js');
 	});
 
 	it('should accept updates from the client and buffer them', async () => {
-		const tsWorker = await createWorker();
+		const { tsWorker, mockEnv } = await createWorker();
 		// Add if statement and remove indentation
 		const changes = [
 			[75, [0, '', ''], 22],
@@ -68,49 +105,60 @@ describe('Typescript Worker', () => {
 		];
 
 		vi.useFakeTimers({ toFake: ['setTimeout', 'queueMicrotask', 'nextTick'] });
-
+		vi.mocked(mockEnv.updateFile).mockReset();
 		for (const change of changes) {
 			tsWorker.updateFile(change as unknown as ChangeSet);
 		}
 
-		expect(tsWorker.getDiagnostics()).toHaveLength(2);
+		expect(mockEnv.updateFile).not.toHaveBeenCalled();
 
 		vi.advanceTimersByTime(1000);
 		vi.runAllTicks();
 
-		expect(tsWorker.getDiagnostics()).toHaveLength(3);
-		expect(tsWorker.getDiagnostics()).toEqual([
+		expect(mockEnv.updateFile).toHaveBeenCalledTimes(1);
+		expect(mockEnv.updateFile).toHaveBeenCalledWith(
+			'id.js',
+			'\n\nif (true){\n  const myObj = {test: "value"}\n}',
 			{
-				from: 10,
-				markClass: 'cm-faded',
-				message: "'myFunction' is declared but its value is never read.",
-				severity: 'warning',
-				to: 20,
+				length: 0,
+				start: 121,
 			},
-			{
-				from: 47,
-				markClass: 'cm-faded',
-				message: "'myObj' is declared but its value is never read.",
-				severity: 'warning',
-				to: 52,
-			},
-			{
-				from: 96,
-				markClass: 'cm-faded',
-				message: "'myObj' is declared but its value is never read.",
-				severity: 'warning',
-				to: 101,
-			},
-		]);
+		);
 	});
 
 	it('should return completions', async () => {
 		const doc = 'return $input.';
-		const tsWorker = await createWorker({ doc });
+		const { tsWorker, mockEnv } = await createWorker({ doc });
+
+		vi.mocked(mockEnv.languageService.getCompletionsAtPosition).mockReturnValue(
+			mock<ts.CompletionInfo>({
+				isGlobalCompletion: false,
+				optionalReplacementSpan: '',
+				entries: [
+					mock<ts.CompletionEntry>({
+						name: 'all',
+						kind: ts.ScriptElementKind.functionElement,
+						sortText: '10',
+					}),
+					mock<ts.CompletionEntry>({
+						name: 'first',
+						kind: ts.ScriptElementKind.functionElement,
+						sortText: '10',
+					}),
+				],
+			}),
+		);
 
 		const completionResult = await tsWorker.getCompletionsAtPos(doc.length);
 		assert(completionResult !== null);
 
+		expect(completionResult).toEqual({
+			isGlobal: false,
+			result: expect.objectContaining({
+				from: 60,
+			}),
+		});
+
 		const completionLabels = completionResult.result.options.map((c) => c.label);
 		expect(completionLabels).toContain('all()');
 		expect(completionLabels).toContain('first()');