1 files changed, 51 insertions, 0 deletions
diff --git a/js/src/tests/test262/prs/3994/built-ins/Uint8Array/prototype/toBase64/option-coercion.js b/js/src/tests/test262/prs/3994/built-ins/Uint8Array/prototype/toBase64/option-coercion.js
new file mode 100644
index 0000000000..054a3a5e0d
--- /dev/null
+++ b/js/src/tests/test262/prs/3994/built-ins/Uint8Array/prototype/toBase64/option-coercion.js
@@ -0,0 +1,51 @@
+// |reftest| shell-option(--enable-uint8array-base64) skip-if(!Uint8Array.fromBase64||!xulRuntime.shell) -- uint8array-base64 is not enabled unconditionally, requires shell-options
+// Copyright (C) 2024 Kevin Gibbons. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-uint8array.prototype.tobase64
+description: Uint8Array.prototype.toBase64 triggers effects of the "alphabet" getter, but does not perform toString on the result
+features: [uint8array-base64, TypedArray]
+---*/
+
+assert.throws(TypeError, function() {
+  (new Uint8Array(2)).toBase64({ alphabet: Object("base64") });
+});
+
+
+var toStringCalls = 0;
+var throwyToString = {
+  toString: function() {
+    toStringCalls += 1;
+    throw new Test262Error("toString called on alphabet value");
+  }
+};
+assert.throws(TypeError, function() {
+  (new Uint8Array(2)).toBase64({ alphabet: throwyToString });
+});
+assert.sameValue(toStringCalls, 0);
+
+var alphabetAccesses = 0;
+var base64UrlOptions = {};
+Object.defineProperty(base64UrlOptions, "alphabet", {
+  get: function() {
+    alphabetAccesses += 1;
+    return "base64url";
+  }
+});
+assert.sameValue((new Uint8Array([199, 239, 242])).toBase64(base64UrlOptions), "x-_y");
+assert.sameValue(alphabetAccesses, 1);
+
+// side-effects from the getter on the receiver are reflected in the result
+var array = new Uint8Array([0]);
+var receiverMutatingOptions = {};
+Object.defineProperty(receiverMutatingOptions, "alphabet", {
+  get: function() {
+    array[0] = 255;
+    return "base64";
+  }
+});
+var result = array.toBase64(receiverMutatingOptions);
+assert.sameValue(result, "/w==");
+assert.sameValue(array[0], 255);
+
+reportCompare(0, 0);