test: add else and error case for TextDecoder

add test for tinyurl.com/codeandlearn-encoding-1
add test for tinyurl.com/codeandlearn-encoding-2

PR-URL: nodejs#24162
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/parallel/test-whatwg-encoding-textdecoder-fatal.js

@@ -88,3 +88,15 @@ bad.forEach((t) => {
   assert(!new TextDecoder().fatal);
   assert(new TextDecoder('utf-8', { fatal: true }).fatal);
 }
+
+{
+  const notArrayBufferViewExamples = [false, {}, 1, '', new Error()];
+  notArrayBufferViewExamples.forEach((invalidInputType) => {
+    common.expectsError(() => {
+      new TextDecoder(undefined, null).decode(invalidInputType);
+    }, {
+      code: 'ERR_INVALID_ARG_TYPE',
+      type: TypeError
+    });
+  });
+}

test/parallel/test-whatwg-encoding-textdecoder.js

@@ -75,6 +75,14 @@ if (common.hasIntl) {
     });
 }
 
+// Test TextDecoder, label undefined, options null
+{
+  const dec = new TextDecoder(undefined, null);
+  assert.strictEqual(dec.encoding, 'utf-8');
+  assert.strictEqual(dec.fatal, false);
+  assert.strictEqual(dec.ignoreBOM, false);
+}
+
 // Test TextDecoder, UTF-16le
 {
   const dec = new TextDecoder('utf-16le');