After review

Author: thomashohn

lib/codecept.js

@@ -194,20 +194,15 @@ class Codecept {
   }
 
   /**
-   * Fisher-Yates algorithm for shuffle
+   * Fisher–Yates shuffle (non-mutating)
    */
-  shuffle(arrayToShuffle) {
-    var i = arrayToShuffle.length,
-      j,
-      temp
-    while (--i > 0) {
-      j = Math.floor(Math.random() * (i + 1))
-      temp = arrayToShuffle[j]
-      arrayToShuffle[j] = arrayToShuffle[i]
-      arrayToShuffle[i] = temp
+  shuffle(array) {
+    const arr = [...array] // clone to avoid mutating input
+    for (let i = arr.length - 1; i > 0; i--) {
+      const j = Math.floor(Math.random() * (i + 1))
+      ;[arr[i], arr[j]] = [arr[j], arr[i]] // swap
     }
-
-    return arrayToShuffle
+    return arr
   }
 
   /**