diff --git a/apps/tests/package.json b/apps/tests/package.json
index 3dac807c..89faa1f8 100644
--- a/apps/tests/package.json
+++ b/apps/tests/package.json
@@ -5,7 +5,7 @@
   "type": "module",
   "description": "nx.js API tests",
   "scripts": {
-    "build": "esbuild --bundle --sourcemap --sources-content=false --target=es2022 --format=esm --outdir=romfs src/main.ts",
+    "build": "esbuild --bundle --sourcemap --sources-content=false --target=es2022 --format=esm --outdir=romfs --define:process.env.NXJS=\\\"1\\\" src/main.ts",
     "nro": "nxjs-nro",
     "nsp": "nxjs-nsp"
   },
diff --git a/apps/tests/src/crypto.test.ts b/apps/tests/src/crypto.test.ts
index 1b05e442..81342fef 100644
--- a/apps/tests/src/crypto.test.ts
+++ b/apps/tests/src/crypto.test.ts
@@ -1,35 +1,9 @@
 import { suite } from 'uvu';
 import * as assert from 'uvu/assert';
+import { toHex, fromHex, concat } from './util.ts';
 
 const test = suite('crypto');
 
-const isNXJS = typeof Switch !== 'undefined';
-
-function toHex(arr: ArrayBuffer) {
-	return Array.from(new Uint8Array(arr))
-		.map((v) => v.toString(16).padStart(2, '0'))
-		.join('');
-}
-
-function fromHex(hex: string): ArrayBuffer {
-	const arr = new Uint8Array(hex.length / 2);
-	for (let i = 0; i < hex.length; i += 2) {
-		arr[i / 2] = parseInt(hex.substr(i, 2), 16);
-	}
-	return arr.buffer;
-}
-
-function concat(...buffers: ArrayBuffer[]): ArrayBuffer {
-	const size = buffers.reduce((acc, buf) => acc + buf.byteLength, 0);
-	let offset = 0;
-	const result = new Uint8Array(size);
-	for (const buf of buffers) {
-		result.set(new Uint8Array(buf), offset);
-		offset += buf.byteLength;
-	}
-	return result.buffer;
-}
-
 test('`crypto.getRandomValues()`', () => {
 	const arr = new Uint8Array(5);
 	assert.equal(toHex(arr.buffer), '0000000000');
@@ -234,7 +208,7 @@ test("`crypto.subtle.decrypt()` with 'AES-CBC' algorithm, 256-bit key", async ()
 });
 
 // Non-standard APIs that are only going to work on nx.js
-if (isNXJS) {
+if (process.env.NXJS === '1') {
 	test("`crypto.subtle.importKey()` with 'raw' format and 'AES-XTS' algorithm, two 128-bit keys", async () => {
 		const key0 = fromHex('0a316b344a7bc7b4db239c61017b86f7');
 		const key1 = fromHex('cc4f4df7cb2becb9a307bb17e8eb01f3');
diff --git a/apps/tests/src/types.d.ts b/apps/tests/src/types.d.ts
new file mode 100644
index 00000000..d246d367
--- /dev/null
+++ b/apps/tests/src/types.d.ts
@@ -0,0 +1,8 @@
+/**
+ * `NXJS` env var is defined via esbuild's `--define` option.
+ */
+declare var process: {
+	env: {
+		NXJS: string;
+	};
+};
diff --git a/apps/tests/src/util.ts b/apps/tests/src/util.ts
new file mode 100644
index 00000000..331ff864
--- /dev/null
+++ b/apps/tests/src/util.ts
@@ -0,0 +1,24 @@
+export function toHex(arr: ArrayBuffer): string {
+	return Array.from(new Uint8Array(arr))
+		.map((v) => v.toString(16).padStart(2, '0'))
+		.join('');
+}
+
+export function fromHex(hex: string): ArrayBuffer {
+	const arr = new Uint8Array(hex.length / 2);
+	for (let i = 0; i < hex.length; i += 2) {
+		arr[i / 2] = parseInt(hex.substr(i, 2), 16);
+	}
+	return arr.buffer;
+}
+
+export function concat(...buffers: ArrayBuffer[]): ArrayBuffer {
+	const size = buffers.reduce((acc, buf) => acc + buf.byteLength, 0);
+	let offset = 0;
+	const result = new Uint8Array(size);
+	for (const buf of buffers) {
+		result.set(new Uint8Array(buf), offset);
+		offset += buf.byteLength;
+	}
+	return result.buffer;
+}
diff --git a/apps/tests/tsconfig.json b/apps/tests/tsconfig.json
index ca3234f7..18c39416 100644
--- a/apps/tests/tsconfig.json
+++ b/apps/tests/tsconfig.json
@@ -8,6 +8,7 @@
     "forceConsistentCasingInFileNames": true,
     "strict": true,
     "skipLibCheck": true,
+    "allowImportingTsExtensions": true,
     "types": [
       "@nx.js/runtime"
     ]