diff --git a/src/initial.test.js b/src/initial.test.js
new file mode 100644
index 0000000..9b2f7e7
--- /dev/null
+++ b/src/initial.test.js
@@ -0,0 +1,12 @@
+import tap from 'tap';
+
+import { Updux } from './Updux.js';
+
+const foo = new Updux({
+    initial: { root: 'abc' },
+    subduxes: {
+        bar: new Updux({ initial: 123 }),
+    },
+});
+
+tap.same(foo.initial, { root: 'abc', bar: 123 });
diff --git a/src/initial.test.ts b/src/initial.test.ts
deleted file mode 100644
index 4a04e85..0000000
--- a/src/initial.test.ts
+++ /dev/null
@@ -1,15 +0,0 @@
-import { dux } from '.';
-import tap from 'tap';
-
-const foo = dux({
-    initial: { root: 'abc' },
-    coduxes: [
-        dux({ initial: { co: 'works' } }),
-        dux({ initial: { co2: 'works' } }),
-    ],
-    subduxes: {
-        bar: dux({ initial: 123 }),
-    },
-});
-
-tap.same(foo.initial, { root: 'abc', co: 'works', co2: 'works', bar: 123 });