diff --git a/cli/tests/unit_node/string_decoder_test.ts b/cli/tests/unit_node/string_decoder_test.ts
new file mode 100644
index 0000000000..93ff69dc32
--- /dev/null
+++ b/cli/tests/unit_node/string_decoder_test.ts
@@ -0,0 +1,167 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+import { assertEquals } from "../../../test_util/std/testing/asserts.ts";
+import { Buffer } from "node:buffer";
+import { StringDecoder } from "node:string_decoder";
+
+Deno.test({
+  name: "String decoder is encoding utf8 correctly",
+  fn() {
+    let decoder;
+
+    decoder = new StringDecoder("utf8");
+    assertEquals(decoder.write(Buffer.from("E1", "hex")), "");
+    assertEquals(decoder.end(), "\ufffd");
+
+    decoder = new StringDecoder("utf8");
+    assertEquals(decoder.write(Buffer.from("E18B", "hex")), "");
+    assertEquals(decoder.end(), "\ufffd");
+
+    decoder = new StringDecoder("utf8");
+    assertEquals(decoder.write(Buffer.from("\ufffd")), "\ufffd");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("utf8");
+    assertEquals(
+      decoder.write(Buffer.from("\ufffd\ufffd\ufffd")),
+      "\ufffd\ufffd\ufffd",
+    );
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("utf8");
+    assertEquals(decoder.write(Buffer.from("EFBFBDE2", "hex")), "\ufffd");
+    assertEquals(decoder.end(), "\ufffd");
+
+    decoder = new StringDecoder("utf8");
+    assertEquals(decoder.write(Buffer.from("F1", "hex")), "");
+    assertEquals(decoder.write(Buffer.from("41F2", "hex")), "\ufffdA");
+    assertEquals(decoder.end(), "\ufffd");
+  },
+});
+
+Deno.test({
+  name: "String decoder is encoding base64 correctly",
+  fn() {
+    let decoder;
+
+    decoder = new StringDecoder("base64");
+    assertEquals(decoder.write(Buffer.from("E1", "hex")), "");
+    assertEquals(decoder.end(), "4Q==");
+
+    decoder = new StringDecoder("base64");
+    assertEquals(decoder.write(Buffer.from("E18B", "hex")), "");
+    assertEquals(decoder.end(), "4Ys=");
+
+    decoder = new StringDecoder("base64");
+    assertEquals(decoder.write(Buffer.from("\ufffd")), "77+9");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("base64");
+    assertEquals(
+      decoder.write(Buffer.from("\ufffd\ufffd\ufffd")),
+      "77+977+977+9",
+    );
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("base64");
+    assertEquals(decoder.write(Buffer.from("EFBFBDE2", "hex")), "77+9");
+    assertEquals(decoder.end(), "4g==");
+
+    decoder = new StringDecoder("base64");
+    assertEquals(decoder.write(Buffer.from("F1", "hex")), "");
+    assertEquals(decoder.write(Buffer.from("41F2", "hex")), "8UHy");
+    assertEquals(decoder.end(), "");
+  },
+});
+
+Deno.test({
+  name: "String decoder is encoding hex correctly",
+  fn() {
+    let decoder;
+
+    decoder = new StringDecoder("hex");
+    assertEquals(decoder.write(Buffer.from("E1", "hex")), "e1");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("hex");
+    assertEquals(decoder.write(Buffer.from("E18B", "hex")), "e18b");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("hex");
+    assertEquals(decoder.write(Buffer.from("\ufffd")), "efbfbd");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("hex");
+    assertEquals(
+      decoder.write(Buffer.from("\ufffd\ufffd\ufffd")),
+      "efbfbdefbfbdefbfbd",
+    );
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("hex");
+    assertEquals(decoder.write(Buffer.from("EFBFBDE2", "hex")), "efbfbde2");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder("hex");
+    assertEquals(decoder.write(Buffer.from("F1", "hex")), "f1");
+    assertEquals(decoder.write(Buffer.from("41F2", "hex")), "41f2");
+    assertEquals(decoder.end(), "");
+  },
+});
+
+Deno.test({
+  name:
+    "String decoder with utf8 would handle incomplete character correctly when append",
+  fn() {
+    let decoder;
+    const specialCharactersText = "不完全な文字のテスト";
+    const encodedBuffer = Buffer.from(specialCharactersText);
+
+    decoder = new StringDecoder("utf8");
+    let str = "";
+    str += decoder.write(encodedBuffer.slice(0, 4));
+    assertEquals(str, "不");
+    str += decoder.write(encodedBuffer.slice(4));
+    assertEquals(str, "不完全な文字のテスト");
+
+    decoder = new StringDecoder("utf8");
+    str = "";
+    str += decoder.write(encodedBuffer.slice(0, 4));
+    str += decoder.write(encodedBuffer.slice(5));
+    assertEquals(str, "不�全な文字のテスト");
+  },
+});
+
+Deno.test({
+  name: "String decoder would have default encoding option as utf8",
+  fn() {
+    let decoder;
+
+    decoder = new StringDecoder();
+    assertEquals(decoder.write(Buffer.from("E1", "hex")), "");
+    assertEquals(decoder.end(), "\ufffd");
+
+    decoder = new StringDecoder();
+    assertEquals(decoder.write(Buffer.from("E18B", "hex")), "");
+    assertEquals(decoder.end(), "\ufffd");
+
+    decoder = new StringDecoder();
+    assertEquals(decoder.write(Buffer.from("\ufffd")), "\ufffd");
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder();
+    assertEquals(
+      decoder.write(Buffer.from("\ufffd\ufffd\ufffd")),
+      "\ufffd\ufffd\ufffd",
+    );
+    assertEquals(decoder.end(), "");
+
+    decoder = new StringDecoder();
+    assertEquals(decoder.write(Buffer.from("EFBFBDE2", "hex")), "\ufffd");
+    assertEquals(decoder.end(), "\ufffd");
+
+    decoder = new StringDecoder();
+    assertEquals(decoder.write(Buffer.from("F1", "hex")), "");
+    assertEquals(decoder.write(Buffer.from("41F2", "hex")), "\ufffdA");
+    assertEquals(decoder.end(), "\ufffd");
+  },
+});