Improve getRandomHex

.changeset/curvy-dogs-change.md

@@ -0,0 +1,5 @@
+---
+"@delvtech/drift": patch
+---
+
+Patched `getRandomHex` testing util for better distribution and better byte alignment with odd length prefixes.

packages/drift/src/exports/index.ts

@@ -152,7 +152,7 @@ export {
   type SerializableKey,
 } from "src/utils/createSerializableKey";
 export { extendInstance } from "src/utils/extendInstance";
-export { getRandomHexChar as getRandomHex } from "src/utils/testing/getRandomHex";
+export { getRandomHex } from "src/utils/testing/getRandomHex";
 export type {
   AnyFunction,
   AnyObject,

packages/drift/src/utils/testing/getRandomHex.test.ts

@@ -0,0 +1,43 @@
+import { getRandomHex } from "src/exports/testing";
+import { describe, expect, it } from "vitest";
+
+describe("getRandomHex", () => {
+  it(
+    "creates valid hex strings",
+    {
+      repeats: 20,
+    },
+    () => {
+      const hex = getRandomHex();
+      expect(hex).toMatch(/^0x[0-9a-f]+$/);
+    },
+  );
+
+  it(
+    "creates a valid hex string with a given byte length",
+    {
+      repeats: 20,
+    },
+    () => {
+      const bytes = Math.floor(Math.random() * 127) + 1;
+      const hex = getRandomHex(bytes);
+      expect(hex.length).toBe(bytes * 2 + 2);
+      expect(hex).toMatch(/^0x[0-9a-f]+$/);
+    },
+  );
+
+  const prefix = "abcde";
+  it(
+    `maintains the correct byte length when provided a prefix ("${prefix}")`,
+    {
+      repeats: 20,
+    },
+    () => {
+      const bytes = Math.floor(Math.random() * 108) + 20;
+      const hex = getRandomHex(bytes, prefix);
+      expect(hex.length).toBe(bytes * 2 + 2);
+      const generatedChars = hex.slice(2 + prefix.length);
+      expect(generatedChars).toMatch(/^[0-9a-f]+$/);
+    },
+  );
+});

packages/drift/src/utils/testing/getRandomHex.ts

@@ -12,14 +12,11 @@ import type { HexString } from "src/adapter/types/Abi";
  * ```
  */
 export function getRandomHex(bytes = 32, prefix = ""): HexString {
-  let hex = prefix;
-  const length = bytes * 2 - prefix.length;
-  for (let i = 0; i < length; i++) {
-    hex += getRandomHexChar();
-  }
-  return `0x${hex}`;
-}
-
-export function getRandomHexChar() {
-  return Math.floor(Math.random() * 16).toString(16);
+  const array = new Uint8Array(bytes);
+  crypto.getRandomValues(array);
+  const hex = Array.from(array, (b) => b.toString(16).padStart(2, "0")).join(
+    "",
+  );
+  const paddedPrefix = prefix.length % 2 ? `${prefix}0` : prefix;
+  return `0x${paddedPrefix}${hex.slice(paddedPrefix.length)}` as HexString;
 }