diff --git a/packages/extension/src/endoify.test.ts b/packages/extension/src/endoify.test.ts
new file mode 100644
index 000000000..8b8c02a43
--- /dev/null
+++ b/packages/extension/src/endoify.test.ts
@@ -0,0 +1,44 @@
+/* eslint-disable @typescript-eslint/explicit-function-return-type */
+import endoified from '@ocap/test-utils/endoified';
+import { describe } from 'vitest';
+import * as vitest from 'vitest';
+
+/* eslint-disable vitest/valid-describe-callback */
+describe(
+  `endoify`,
+  endoified(
+    // eslint-disable-next-line @typescript-eslint/no-shadow
+    ({ it, expect }) => {
+      for (const assertion of [
+        () => typeof globalThis === 'object',
+        () => typeof lockdown === 'function',
+        () => typeof repairIntrinsics === 'function',
+        () => typeof Compartment === 'function',
+        () => typeof assert === 'function',
+        () => typeof HandledPromise === 'function',
+        () => typeof harden === 'function',
+        () => typeof getStackString === 'function',
+        () => {
+          try {
+            return !Object.assign(harden({ a: 1 }), { b: 2 });
+          } catch {
+            return true;
+          }
+        },
+      ]) {
+        it(`asserts ${String(assertion)}`, () => {
+          console.log(`${String(assertion)} => ${assertion()}`);
+          expect(assertion(), `${String(assertion)}`).toBe(true);
+        });
+      }
+    },
+    { ...vitest },
+  ),
+);
+
+declare global {
+  // eslint-disable-next-line no-var
+  var getStackString: (error: Error) => string;
+  // eslint-disable-next-line no-var, @typescript-eslint/consistent-type-imports
+  var HandledPromise: import('@endo/eventual-send').HandledPromiseConstructor;
+}
diff --git a/packages/extension/vite.config.ts b/packages/extension/vite.config.ts
index 7d5e5d364..eccec9946 100644
--- a/packages/extension/vite.config.ts
+++ b/packages/extension/vite.config.ts
@@ -29,9 +29,6 @@ const staticCopyTargets: readonly string[] = [
   // External modules
   'dev-console.js',
   '../../shims/dist/endoify.mjs',
-  // Dependencies of external modules
-  '../../shims/dist/eventual-send.mjs',
-  '../../../node_modules/ses/dist/ses.mjs',
 ];
 
 // https://vitejs.dev/config/
diff --git a/packages/shims/scripts/bundle.js b/packages/shims/scripts/bundle.js
index 45157d98d..76e1d4cd4 100644
--- a/packages/shims/scripts/bundle.js
+++ b/packages/shims/scripts/bundle.js
@@ -1,42 +1,56 @@
+// eslint-disable-next-line import-x/no-unassigned-import
 import 'ses';
+// eslint-disable-next-line import-x/no-unassigned-import, import-x/extensions
 import '@endo/lockdown/commit.js';
 
 import bundleSource from '@endo/bundle-source';
-import { copyFile, mkdir, writeFile } from 'fs/promises';
+import { mkdir, writeFile } from 'fs/promises';
 import path from 'path';
 import { rimraf } from 'rimraf';
 import { fileURLToPath } from 'url';
 
 console.log('Bundling shims...');
 
-const rootDir = path.resolve(import.meta.dirname, '..');
+const rootDir = fileURLToPath(new URL('..', import.meta.url));
 const src = path.resolve(rootDir, 'src');
 const dist = path.resolve(rootDir, 'dist');
+
+await mkdir(dist, { recursive: true });
+await rimraf(`${dist}/*`, { glob: true });
+
 const fileNames = {
   endoify: 'endoify.mjs',
-  eventualSend: 'eventual-send.mjs',
-  applyLockdown: 'apply-lockdown.mjs',
 };
 
-await mkdir(dist, { recursive: true });
-await rimraf(`${dist}/*`);
+const { source: endoifyBundleSource } = await bundleSource(
+  path.resolve(src, fileNames.endoify),
+  { format: 'endoScript' },
+);
 
-for (const fileName of [fileNames.endoify, fileNames.applyLockdown]) {
-  await copyFile(path.resolve(src, fileName), path.resolve(dist, fileName));
-}
+await writeFile(path.resolve(dist, fileNames.endoify), endoifyBundleSource);
 
-const eventualSendSourcePath = fileURLToPath(
-  import.meta.resolve('@endo/eventual-send/shim.js'),
-);
+// const fileNames = {
+//   endoify: 'endoify.mjs',
+//   eventualSend: 'eventual-send.mjs',
+//   applyLockdown: 'apply-lockdown.mjs',
+// };
 
-const { source: eventualSendBundleSource } = await bundleSource(
-  eventualSendSourcePath,
-  { format: 'endoScript' },
-);
+// for (const fileName of [fileNames.endoify, fileNames.applyLockdown]) {
+//   await copyFile(path.resolve(src, fileName), path.resolve(dist, fileName));
+// }
 
-await writeFile(
-  path.resolve(dist, fileNames.eventualSend),
-  eventualSendBundleSource,
-);
+// const eventualSendSourcePath = fileURLToPath(
+//   import.meta.resolve('@endo/eventual-send/shim.js'),
+// );
+
+// const { source: eventualSendBundleSource } = await bundleSource(
+//   eventualSendSourcePath,
+//   { format: 'endoScript' },
+// );
+
+// await writeFile(
+//   path.resolve(dist, fileNames.eventualSend),
+//   eventualSendBundleSource,
+// );
 
 console.log('Success!');
diff --git a/packages/shims/src/apply-lockdown.mjs b/packages/shims/src/apply-lockdown.mjs
deleted file mode 100644
index e01804d3a..000000000
--- a/packages/shims/src/apply-lockdown.mjs
+++ /dev/null
@@ -1,11 +0,0 @@
-import './ses.mjs';
-
-lockdown({
-  consoleTaming: 'unsafe',
-  dateTaming: 'unsafe',
-  domainTaming: 'unsafe',
-  errorTaming: 'unsafe',
-  mathTaming: 'unsafe',
-  overrideTaming: 'severe',
-  stackFiltering: 'verbose',
-});
diff --git a/packages/shims/src/endoify.mjs b/packages/shims/src/endoify.mjs
index 824aa9c32..2208eeac8 100644
--- a/packages/shims/src/endoify.mjs
+++ b/packages/shims/src/endoify.mjs
@@ -1,5 +1,5 @@
-import './ses.mjs';
-import './eventual-send.mjs';
+import 'ses';
+import '@endo/eventual-send/shim.js';
 
 lockdown({
   consoleTaming: 'unsafe',
diff --git a/packages/test-utils/package.json b/packages/test-utils/package.json
index c239be901..c577ca1f2 100644
--- a/packages/test-utils/package.json
+++ b/packages/test-utils/package.json
@@ -10,6 +10,7 @@
   "type": "module",
   "exports": {
     ".": "./src/index.ts",
+    "./endoified": "./src/endoified.ts",
     "./package.json": "./package.json"
   },
   "scripts": {
@@ -17,6 +18,7 @@
     "test": "echo 'No tests.' && exit 0"
   },
   "devDependencies": {
+    "jsdom": "^24.1.1",
     "rimraf": "^6.0.1",
     "ses": "^1.7.0",
     "typescript": "~4.9.5",
diff --git a/packages/test-utils/src/endoified.ts b/packages/test-utils/src/endoified.ts
new file mode 100644
index 000000000..a3cbb64d7
--- /dev/null
+++ b/packages/test-utils/src/endoified.ts
@@ -0,0 +1,78 @@
+/* eslint-disable n/no-sync */
+import jsdom from 'jsdom';
+import { spawnSync } from 'node:child_process';
+import { readFileSync, existsSync } from 'node:fs';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const endoifyBundleSourceTextURL = new URL(
+  '../../shims/dist/endoify.mjs',
+  import.meta.url.replace(/^https?:\/\/.*?\/@fs\//u, 'file:///'),
+);
+const endoifyShimsBundleSourceLocation = fileURLToPath(
+  endoifyBundleSourceTextURL.href,
+);
+
+/**
+ * Run an endoified test with endowments.
+ *
+ * @param test - The test to run. It must be a synchronous function that takes `endowments` as its only parameter.
+ * @param endowments - Endowments passed to the test. They must include `vitest` capabilities like `it` and `expect`.
+ * @param endoifySourceLocation - Optional path to the endoify bundle. It must either be absolute or relative to `process.cwd()`.
+ * @returns The return value of the test.
+ */
+export default function endoified<
+  // eslint-disable-next-line @typescript-eslint/consistent-type-imports
+  Endowments extends Partial<typeof import('vitest')>,
+>(
+  test: (endowments: Endowments) => void,
+  endowments: Endowments,
+  endoifySourceLocation?: string | URL,
+): () => void {
+  return () => {
+    // console.log({ endoifySourceLocation: `${endoifySourceLocation}` });
+
+    const absoluteEndoifySourcePath =
+      // eslint-disable-next-line no-nested-ternary
+      endoifySourceLocation && typeof endoifySourceLocation === 'string'
+        ? endoifySourceLocation
+        : endoifySourceLocation && endoifySourceLocation instanceof URL
+        ? fileURLToPath(endoifySourceLocation.href)
+        : endoifyShimsBundleSourceLocation;
+
+    const relativeEndoifySourcePath = path.relative(
+      '.',
+      absoluteEndoifySourcePath,
+    );
+
+    if (
+      absoluteEndoifySourcePath === endoifyShimsBundleSourceLocation &&
+      !existsSync(endoifyShimsBundleSourceLocation)
+    ) {
+      spawnSync(
+        'node',
+        [
+          fileURLToPath(
+            new URL(
+              '../../shims/scripts/bundle.js',
+              import.meta.url.replace(/^https?:\/\/.*?\/@fs\//u, 'file:///'),
+            ).href,
+          ),
+        ],
+        { stdio: 'inherit' },
+      );
+    }
+
+    // console.log({ relativeEndoifySourcePath });
+
+    const evaluatorSourceText = String(test);
+    const endoifySourceText = readFileSync(relativeEndoifySourcePath, 'utf-8');
+
+    // console.log({ endoifySourceText });
+
+    const dom = new jsdom.JSDOM(``, { runScripts: 'outside-only' });
+
+    dom.window.eval(endoifySourceText);
+    (dom.window.eval(evaluatorSourceText) as typeof test)(endowments);
+  };
+}
diff --git a/yarn.lock b/yarn.lock
index d5df286f8..9a9bbcf84 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1357,6 +1357,7 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@ocap/test-utils@workspace:packages/test-utils"
   dependencies:
+    jsdom: "npm:^24.1.1"
     rimraf: "npm:^6.0.1"
     ses: "npm:^1.7.0"
     typescript: "npm:~4.9.5"