diff --git a/packages/runtimes/js/test/esm-js-loader-retry.test.cjs b/packages/runtimes/js/test/esm-js-loader-retry.test.cjs
deleted file mode 100644
index 564b1751b..000000000
--- a/packages/runtimes/js/test/esm-js-loader-retry.test.cjs
+++ /dev/null
@@ -1,62 +0,0 @@
-// @ts-check
-const load = require('../src/helpers/browser/esm-js-loader-retry.js')
-const bundleManifest  = require( '../src/helpers/bundle-manifest.js')
-const { mock }  = require( 'node:test')
-const assert  = require( 'node:assert')
-
-// eslint-disable-next-line require-await
-const importError = async () => {
-  throw new Error('TypeError: Failed to fetch dynamically imported module')
-}
-
-describe('esm-js-loader-retry', () => {
-  /** @type {import('node:test').Mock} */
-  let mockSetTimeout
-
-  /** @type {import('node:test').Mock} */
-  let mockParcelImport
-
-  before(() => {
-    bundleManifest.register('http://localhost', ['1', 'foo.js'])
-  })
-
-  beforeEach(() => {
-    mockSetTimeout = mock.fn((callback) => callback())
-    globalThis.setTimeout = mockSetTimeout
-
-    mockParcelImport = mock.fn()
-    globalThis.__parcel__import__ = mockParcelImport
-
-    globalThis.parcelRequire = mock.fn()
-    globalThis.navigator = { onLine: true }
-    globalThis.dispatchEvent = mock.fn()
-  })
-
-  it('should not throw', async () => {
-    await assert.doesNotReject(() => load('1'))
-  })
-
-  it('should throw if all requests fail', async () => {
-    mockParcelImport.mock.mockImplementationOnce(importError, 0)
-    mockParcelImport.mock.mockImplementationOnce(importError, 1)
-    mockParcelImport.mock.mockImplementationOnce(importError, 2)
-    mockParcelImport.mock.mockImplementationOnce(importError, 3)
-    mockParcelImport.mock.mockImplementationOnce(importError, 4)
-    mockParcelImport.mock.mockImplementationOnce(importError, 5)
-    mockParcelImport.mock.mockImplementationOnce(importError, 6)
-    await assert.rejects(() => load('1'))
-  })
-
-  it('should resolve if the first request fails', async () => {
-    mockParcelImport.mock.mockImplementationOnce(importError, 0)
-    await assert.doesNotReject(() => load('1'))
-  })
-
-  it('should resolve if the first few requests fails', async () => {
-    mockParcelImport.mock.mockImplementationOnce(importError, 0)
-    mockParcelImport.mock.mockImplementationOnce(importError, 1)
-    mockParcelImport.mock.mockImplementationOnce(importError, 2)
-    mockParcelImport.mock.mockImplementationOnce(importError, 3)
-    await assert.doesNotReject(() => load('1'))
-  })
-})
diff --git a/packages/runtimes/js/test/esm-js-loader-retry.test.ts b/packages/runtimes/js/test/esm-js-loader-retry.test.ts
new file mode 100644
index 000000000..fcaae702d
--- /dev/null
+++ b/packages/runtimes/js/test/esm-js-loader-retry.test.ts
@@ -0,0 +1,63 @@
+import load from '../src/helpers/browser/esm-js-loader-retry.js';
+import bundleManifest from '../src/helpers/bundle-manifest.js';
+import {mock, Mock} from 'node:test';
+import assert from 'node:assert';
+
+declare var globalThis: Window & {[key: string]: any};
+
+describe('esm-js-loader-retry', () => {
+  let mockSetTimeout: Mock<Window['setTimeout']>;
+  let mockParcelImport: Mock<() => Promise<void>>;
+
+  // eslint-disable-next-line require-await
+  const importError = async () => {
+    throw new Error('TypeError: Failed to fetch dynamically imported module');
+  };
+
+  before(() => {
+    bundleManifest.register('http://localhost', ['1', 'foo.js']);
+  });
+
+  beforeEach(() => {
+    mockSetTimeout = mock.fn((callback: any, duration: any, ...args: any[]) =>
+      callback(),
+    );
+    globalThis.setTimeout = mockSetTimeout;
+
+    mockParcelImport = mock.fn(() => Promise.resolve());
+    globalThis.__parcel__import__ = mockParcelImport;
+
+    globalThis.parcelRequire = mock.fn();
+    // @ts-expect-error
+    globalThis.navigator = {onLine: true};
+    globalThis.dispatchEvent = mock.fn();
+  });
+
+  it('should not throw', async () => {
+    await assert.doesNotReject(() => load('1'));
+  });
+
+  it('should throw if all requests fail', async () => {
+    mockParcelImport.mock.mockImplementationOnce(importError, 0);
+    mockParcelImport.mock.mockImplementationOnce(importError, 1);
+    mockParcelImport.mock.mockImplementationOnce(importError, 2);
+    mockParcelImport.mock.mockImplementationOnce(importError, 3);
+    mockParcelImport.mock.mockImplementationOnce(importError, 4);
+    mockParcelImport.mock.mockImplementationOnce(importError, 5);
+    mockParcelImport.mock.mockImplementationOnce(importError, 6);
+    await assert.rejects(() => load('1'));
+  });
+
+  it('should resolve if the first request fails', async () => {
+    mockParcelImport.mock.mockImplementationOnce(importError, 0);
+    await assert.doesNotReject(() => load('1'));
+  });
+
+  it('should resolve if the first few requests fails', async () => {
+    mockParcelImport.mock.mockImplementationOnce(importError, 0);
+    mockParcelImport.mock.mockImplementationOnce(importError, 1);
+    mockParcelImport.mock.mockImplementationOnce(importError, 2);
+    mockParcelImport.mock.mockImplementationOnce(importError, 3);
+    await assert.doesNotReject(() => load('1'));
+  });
+});