diff --git a/package.json b/package.json
index 47536d4..78a64b7 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
     "test:dist": "npm run lint && npm run test && npm run test:browser && npm run test:deno",
     "test:cover": "npm run cover:clean && npx nyc --no-clean npm run 'test' && npm run cover:report",
     "test:deno": "deno test test/deno_test.ts",
-    "test:fuzz": "npm exec --yes -- jsfuzz@git+https://gitlab.com/gitlab-org/security-products/analyzers/fuzzers/jsfuzz.git --fuzzTime 60 --no-versifier test/decode.jsfuzz.js corpus",
+    "test:fuzz": "npm exec --yes -- jsfuzz@git+https://gitlab.com/gitlab-org/security-products/analyzers/fuzzers/jsfuzz.git#39e6cf16613a0e30c7a7953f62e64292dbd5d3f3 --fuzzTime 60 --no-versifier test/decode.jsfuzz.js corpus",
     "cover:clean": "rimraf .nyc_output coverage/",
     "cover:report": "npx nyc report --reporter=text-summary --reporter=html --reporter=json",
     "test:browser": "karma start --single-run",
diff --git a/test/CachedKeyDecoder.test.ts b/test/CachedKeyDecoder.test.ts
index 09f5842..eaee6c8 100644
--- a/test/CachedKeyDecoder.test.ts
+++ b/test/CachedKeyDecoder.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { CachedKeyDecoder, KeyDecoder } from "../src/CachedKeyDecoder";
 import { utf8EncodeJs, utf8Count } from "../src/utils/utf8";
 
diff --git a/test/ExtensionCodec.test.ts b/test/ExtensionCodec.test.ts
index 21ae8db..48d4173 100644
--- a/test/ExtensionCodec.test.ts
+++ b/test/ExtensionCodec.test.ts
@@ -1,5 +1,5 @@
-import assert from "assert";
-import util from "util";
+import assert from "node:assert";
+import util from "node:util";
 import { encode, decode, ExtensionCodec, decodeAsync } from "../src";
 
 describe("ExtensionCodec", () => {
diff --git a/test/bigint64.test.ts b/test/bigint64.test.ts
index fabf0f5..10e2a65 100644
--- a/test/bigint64.test.ts
+++ b/test/bigint64.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decode } from "../src";
 
 describe("useBigInt64: true", () => {
diff --git a/test/codec-bigint.test.ts b/test/codec-bigint.test.ts
index 4ed6aff..0a9ef27 100644
--- a/test/codec-bigint.test.ts
+++ b/test/codec-bigint.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decode, ExtensionCodec, DecodeError } from "../src";
 
 // There's a built-in `useBigInt64: true` option, but a custom codec might be
diff --git a/test/codec-float.test.ts b/test/codec-float.test.ts
index 6b55df7..050c563 100644
--- a/test/codec-float.test.ts
+++ b/test/codec-float.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { decode } from "../src";
 import * as ieee754 from "ieee754";
 
diff --git a/test/codec-int.test.ts b/test/codec-int.test.ts
index 486f93b..2d4d611 100644
--- a/test/codec-int.test.ts
+++ b/test/codec-int.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { setInt64, getInt64, getUint64, setUint64 } from "../src/utils/int";
 
 const INT64SPECS = {
diff --git a/test/codec-timestamp.test.ts b/test/codec-timestamp.test.ts
index de4f707..a3927a6 100644
--- a/test/codec-timestamp.test.ts
+++ b/test/codec-timestamp.test.ts
@@ -1,5 +1,5 @@
-import assert from "assert";
-import util from "util";
+import assert from "node:assert";
+import util from "node:util";
 import {
   encode,
   decode,
diff --git a/test/decode-blob.test.ts b/test/decode-blob.test.ts
index 4c7c536..11e9a8b 100644
--- a/test/decode-blob.test.ts
+++ b/test/decode-blob.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decode, decodeAsync } from "@msgpack/msgpack";
 
 (typeof Blob !== "undefined" ? describe : describe.skip)("Blob", () => {
diff --git a/test/decode-max-length.test.ts b/test/decode-max-length.test.ts
index 7ee2e33..c7489c8 100644
--- a/test/decode-max-length.test.ts
+++ b/test/decode-max-length.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decode, decodeAsync } from "../src";
 import type { DecoderOptions } from "../src";
 
diff --git a/test/decode.jsfuzz.js b/test/decode.jsfuzz.js
index 8dbe634..7341f49 100644
--- a/test/decode.jsfuzz.js
+++ b/test/decode.jsfuzz.js
@@ -1,5 +1,5 @@
 /* eslint-disable */
-const assert = require("assert");
+const assert = require("node:assert");
 const { Decoder, encode, DecodeError } = require("../dist/index.js");
 
 /**
diff --git a/test/decodeArrayStream.test.ts b/test/decodeArrayStream.test.ts
index 0486101..a06ed99 100644
--- a/test/decodeArrayStream.test.ts
+++ b/test/decodeArrayStream.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decodeArrayStream } from "../src";
 
 describe("decodeArrayStream", () => {
diff --git a/test/decodeAsync.test.ts b/test/decodeAsync.test.ts
index 0e8d901..473c167 100644
--- a/test/decodeAsync.test.ts
+++ b/test/decodeAsync.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decodeAsync } from "../src";
 
 describe("decodeAsync", () => {
diff --git a/test/decodeMulti.test.ts b/test/decodeMulti.test.ts
index 346d15c..9d4037d 100644
--- a/test/decodeMulti.test.ts
+++ b/test/decodeMulti.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decodeMulti } from "@msgpack/msgpack";
 
 describe("decodeMulti", () => {
diff --git a/test/decodeMultiStream.test.ts b/test/decodeMultiStream.test.ts
index cef9d6e..9ef379b 100644
--- a/test/decodeMultiStream.test.ts
+++ b/test/decodeMultiStream.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decodeMultiStream } from "@msgpack/msgpack";
 
 describe("decodeStream", () => {
diff --git a/test/edge-cases.test.ts b/test/edge-cases.test.ts
index ca4ad51..f434915 100644
--- a/test/edge-cases.test.ts
+++ b/test/edge-cases.test.ts
@@ -1,6 +1,6 @@
 // kind of hand-written fuzzing data
 // any errors should not break Encoder/Decoder instance states
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decodeAsync, decode, Encoder, Decoder, decodeMulti, decodeMultiStream } from "../src";
 import { DataViewIndexOutOfBoundsError } from "../src/Decoder";
 
diff --git a/test/encode.test.ts b/test/encode.test.ts
index d2679d5..71a0799 100644
--- a/test/encode.test.ts
+++ b/test/encode.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decode } from "@msgpack/msgpack";
 
 describe("encode", () => {
diff --git a/test/msgpack-ext.test.ts b/test/msgpack-ext.test.ts
index 73a536a..fc96f80 100644
--- a/test/msgpack-ext.test.ts
+++ b/test/msgpack-ext.test.ts
@@ -1,4 +1,4 @@
-import assert from "assert";
+import assert from "node:assert";
 import { encode, decode, ExtData } from "../src";
 
 function seq(n: number) {
diff --git a/test/msgpack-test-suite.test.ts b/test/msgpack-test-suite.test.ts
index 6800973..891c62c 100644
--- a/test/msgpack-test-suite.test.ts
+++ b/test/msgpack-test-suite.test.ts
@@ -1,5 +1,5 @@
-import assert from "assert";
-import util from "util";
+import assert from "node:assert";
+import util from "node:util";
 import { Exam } from "msgpack-test-js";
 import { MsgTimestamp } from "msg-timestamp";
 import { encode, decode, ExtensionCodec, EXT_TIMESTAMP, encodeTimeSpecToTimestamp } from "@msgpack/msgpack";
diff --git a/test/prototype-pollution.test.ts b/test/prototype-pollution.test.ts
index bc15b63..f73f383 100644
--- a/test/prototype-pollution.test.ts
+++ b/test/prototype-pollution.test.ts
@@ -1,4 +1,4 @@
-import { throws } from "assert";
+import { throws } from "node:assert";
 import { encode, decode, DecodeError } from "@msgpack/msgpack";
 
 describe("prototype pollution", () => {
diff --git a/test/readme.test.ts b/test/readme.test.ts
index fea8123..ea47b11 100644
--- a/test/readme.test.ts
+++ b/test/readme.test.ts
@@ -1,4 +1,4 @@
-import { deepStrictEqual } from "assert";
+import { deepStrictEqual } from "node:assert";
 import { encode, decode } from "@msgpack/msgpack";
 
 describe("README", () => {
diff --git a/test/reuse-instances.test.ts b/test/reuse-instances.test.ts
index 29a0b78..9930d81 100644
--- a/test/reuse-instances.test.ts
+++ b/test/reuse-instances.test.ts
@@ -1,4 +1,4 @@
-import { deepStrictEqual } from "assert";
+import { deepStrictEqual } from "node:assert";
 import { Encoder, Decoder, decode } from "@msgpack/msgpack";
 
 const createStream = async function* (...args: any) {
diff --git a/test/whatwg-streams.test.ts b/test/whatwg-streams.test.ts
index 7a83805..8660264 100644
--- a/test/whatwg-streams.test.ts
+++ b/test/whatwg-streams.test.ts
@@ -1,4 +1,4 @@
-import { deepStrictEqual } from "assert";
+import { deepStrictEqual } from "node:assert";
 import { decodeAsync, encode, decodeArrayStream } from "@msgpack/msgpack";
 
 const isReadableStreamConstructorAvailable: boolean = (() => {