add test

test/dig/dig.js

@@ -1 +1,11 @@
+const dig = (obj, target) =>
+  target in obj
+    ? obj[target]
+    : Object
+        .values(obj)
+        .reduce((acc, val) => {
+          if (acc !== undefined) return acc;
+          if (typeof val === 'object') return dig(val, target);
+        }, undefined);
+
 module.exports = dig;