Added a test for Array.prototype.flatMap where mapperFunction throws

test/built-ins/Array/prototype/flatMap/mapperfunction-throws.js

@@ -0,0 +1,40 @@
+// Copyright (C) 2026 Garham Lee. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-array.prototype.flatmap
+description: >
+    Array.prototype.flatMap throws when _soucreLen_ is not 0 and _mapperFunction_ throws.
+info: |
+    Array.prototype.flatMap ( _mapperFunction_ [ , _thisArg_ ] )
+
+    1. Let _O_ be ? ToObject(*this* value).
+    2. Let _sourceLen_ be ? LengthOfArrayLike(_O_).
+    5. Perform ? FlattenIntoArray(_A_, _O_, _sourceLen_, 0, 1, _mapperFunction_, _thisArg_).
+
+    FlattenIntoArray (_target_,_source_,_sourceLen_,_start_,_depth_,optional _mapperFunction_,optional _thisArg_,)
+
+    2. Let _targetIndex_ be _start_.
+    3. Let _sourceIndex_ be *+0*<sub>𝔽</sub>.
+    4. Repeat, while ℝ(_sourceIndex_) &lt; _sourceLen_,
+        a. Let _P_ be ! ToString(_sourceIndex_).
+        b. Let _exists_ be ? HasProperty(_source_, _P_).
+        c. If _exists_ is *true*, then
+            i. Let _element_ be ? Get(_source_, _P_).
+            ii. If _mapperFunction_ is present, then
+                1. Set _element_ to ? Call(_mapperFunction_, _thisArg_, « _element_, _sourceIndex_, _source_ »).
+features: [Array.prototype.flatMap]
+---*/
+//Check #1
+assert.throws(Test262Error, function () {
+    [0].flatMap(x => {throw new Test262Error});
+});
+
+//Check #2
+var callcount = 0;
+[].flatMap(() => {
+    callcount += 1;
+    throw new Test262Error;
+});
+
+assert.sameValue(callcount, 0, "If _soucreLen_ is 0, _mapperFunction_ should not be called.")