1 files changed, 35 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/String/prototype/isWellFormed/to-string-primitive.js b/js/src/tests/test262/built-ins/String/prototype/isWellFormed/to-string-primitive.js
new file mode 100644
index 0000000000..5ef95cf21a
--- /dev/null
+++ b/js/src/tests/test262/built-ins/String/prototype/isWellFormed/to-string-primitive.js
@@ -0,0 +1,35 @@
+// |reftest| shell-option(--enable-well-formed-unicode-strings) skip-if(!String.prototype.isWellFormed||!xulRuntime.shell) -- String.prototype.isWellFormed is not enabled unconditionally, requires shell-options
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-string.prototype.iswellformed
+description: >
+  The method should coerce the receiver to a string.
+info: |
+  String.prototype.isWellFormed ( )
+
+  2. Let S be ? ToString(O).
+  …
+
+features: [String.prototype.isWellFormed]
+---*/
+
+const tests = [
+  [true, Boolean.prototype],
+  [1, Number.prototype],
+  [1n, BigInt.prototype],
+];
+
+for (const [v, proto] of tests) {
+  proto.toString = function() {
+    throw new Test262Error(`should not call toString on the prototype for ${typeof v}`);
+  }
+  let result = String.prototype.isWellFormed.call(v);
+  delete proto.toString;
+  assert.sameValue(result, true, `isWellFormed for ${typeof v}`);
+}
+
+Symbol.prototype.toString = function() { throw new TypeError("should not call toString on the prototype for Symbol"); }
+assert.throws(TypeError, () => String.prototype.isWellFormed.call(Symbol()), `Built-in result for Symbol`);
+
+reportCompare(0, 0);