test: convert test_encoding_binding.cc to a JS test

The cctest file `test_encoding_binding.cc` is never tested and it is
not a valid test. Binding functions should never be tested with V8 API
circumvented. A binding function should only be tested with JS calls.

PR-URL: #56791
Refs: #55275
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Daniel Lemire <daniel@lemire.me>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-internal-encoding-binding.js

@@ -0,0 +1,48 @@
+// Flags: --expose-internals
+
+'use strict';
+
+require('../common');
+
+const assert = require('node:assert');
+const { internalBinding } = require('internal/test/binding');
+const binding = internalBinding('encoding_binding');
+
+{
+  // Valid input
+  const buf = Uint8Array.from([0xC1, 0xE9, 0xF3]);
+  assert.strictEqual(binding.decodeLatin1(buf, false, false), 'Áéó');
+}
+
+{
+  // Empty input
+  const buf = Uint8Array.from([]);
+  assert.strictEqual(binding.decodeLatin1(buf, false, false), '');
+}
+
+{
+  // Invalid input, but Latin1 has no invalid chars and should never throw.
+  const buf = new TextEncoder().encode('Invalid Latin1 🧑‍🧑‍🧒‍🧒');
+  assert.strictEqual(
+    binding.decodeLatin1(buf, false, false),
+    'Invalid Latin1 ð\x9F§\x91â\x80\x8Dð\x9F§\x91â\x80\x8Dð\x9F§\x92â\x80\x8Dð\x9F§\x92'
+  );
+}
+
+{
+  // IgnoreBOM with BOM
+  const buf = Uint8Array.from([0xFE, 0xFF, 0xC1, 0xE9, 0xF3]);
+  assert.strictEqual(binding.decodeLatin1(buf, true, false), 'þÿÁéó');
+}
+
+{
+  // Fatal and InvalidInput, but Latin1 has no invalid chars and should never throw.
+  const buf = Uint8Array.from([0xFF, 0xFF, 0xFF]);
+  assert.strictEqual(binding.decodeLatin1(buf, false, true), 'ÿÿÿ');
+}
+
+{
+  // IgnoreBOM and Fatal, but Latin1 has no invalid chars and should never throw.
+  const buf = Uint8Array.from([0xFE, 0xFF, 0xC1, 0xE9, 0xF3]);
+  assert.strictEqual(binding.decodeLatin1(buf, true, true), 'þÿÁéó');
+}