Add test for length conversion

test/built-ins/Array/prototype/group/invalid-object.js

@@ -15,7 +15,7 @@ info: |
 features: [array-grouping]
 ---*/
 
-const throws = () => {
+const throws = function() {
   throw new Test262Error('callback function should not be called')
 };
 

test/built-ins/Array/prototype/group/length-throw.js

@@ -0,0 +1,36 @@
+// Copyright (c) 2021 Ecma International.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-array.prototype.group
+description: Array.prototype.group errors when array-like's length can't be coerced.
+info: |
+  22.1.3.14 Array.prototype.group ( callbackfn [ , thisArg ] )
+
+  ...
+
+  2. Let len be ? LengthOfArrayLike(O).
+
+  ...
+features: [array-grouping]
+---*/
+
+assert.throws(Test262Error, function() {
+  const arrayLike = Object.defineProperty({}, 'length', {
+    get: function() {
+      throw new Test262Error('no length for you');
+    }
+  });
+  Array.prototype.group.call(arrayLike, function() {
+    return 'key';
+  });
+});
+
+assert.throws(TypeError, function() {
+  const arrayLike = {
+    length: 1n,
+  };
+  Array.prototype.group.call(arrayLike, function() {
+    return 'key';
+  });
+});