Test Array.prototype.findLast* length clamping

test/built-ins/Array/prototype/findLast/maximum-index.js

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+// Copyright (C) 2023 Richard Gibson. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-array.prototype.findlast
+description: >
+  Support the maximum valid integer index.
+info: |
+  Array.prototype.findLast ( predicate [ , thisArg ] )
+
+  1. Let O be ? ToObject(this value).
+  2. Let len be ? LengthOfArrayLike(O).
+
+  LengthOfArrayLike ( obj )
+
+  1. Return ℝ(? ToLength(? Get(obj, "length"))).
+
+  ToLength ( argument )
+
+  1. Let len be ? ToIntegerOrInfinity(argument).
+  2. If len ≤ 0, return +0𝔽.
+  3. Return 𝔽(min(len, 2**53 - 1)).
+features: [array-find-from-last]
+---*/
+
+var tooBigLength = Number.MAX_VALUE;
+var maxExpectedIndex = 9007199254740990;
+var arrayLike = { length: tooBigLength };
+var calledWithIndex = [];
+
+Array.prototype.findLast.call(arrayLike, function(_value, index) {
+  calledWithIndex.push(index);
+  return true;
+});
+
+assert.sameValue(calledWithIndex.length, 1, 'predicate invoked once');
+assert.sameValue(calledWithIndex[0], maxExpectedIndex);

test/built-ins/Array/prototype/findLastIndex/maximum-index.js

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+// Copyright (C) 2023 Richard Gibson. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-array.prototype.findlastindex
+description: >
+  Support the maximum valid integer index.
+info: |
+  Array.prototype.findLastIndex ( predicate [ , thisArg ] )
+
+  1. Let O be ? ToObject(this value).
+  2. Let len be ? LengthOfArrayLike(O).
+
+  LengthOfArrayLike ( obj )
+
+  1. Return ℝ(? ToLength(? Get(obj, "length"))).
+
+  ToLength ( argument )
+
+  1. Let len be ? ToIntegerOrInfinity(argument).
+  2. If len ≤ 0, return +0𝔽.
+  3. Return 𝔽(min(len, 2**53 - 1)).
+features: [array-find-from-last]
+---*/
+
+var tooBigLength = Number.MAX_VALUE;
+var maxExpectedIndex = 9007199254740990;
+var arrayLike = { length: tooBigLength };
+var calledWithIndex = [];
+
+Array.prototype.findLastIndex.call(arrayLike, function(_value, index) {
+  calledWithIndex.push(index);
+  return true;
+});
+
+assert.sameValue(calledWithIndex.length, 1, 'predicate invoked once');
+assert.sameValue(calledWithIndex[0], maxExpectedIndex);