Add missing explicit ToString conversion for symbol values and ensure the expected NaN result is a (locale-dependent) string

test/intl402/NumberFormat/prototype/format/default-value.js

@@ -10,8 +10,14 @@ info: |
   11.1.4 Number Format Functions
 
   3. If value is not provided, let value be undefined.
+  4. Let x be ? ToNumber(value).
 ---*/
 
 const nf = new Intl.NumberFormat();
-assert.sameValue(nf.format(), NaN);
+
-assert.sameValue(nf.format(undefined), NaN);
+// In most locales this is string "NaN", but there are exceptions, cf. "ليس رقم"
+// in Arabic, "epäluku" in Finnish, "не число" in Russian, "son emas" in Uzbek etc.
+const resultNaN = nf.format(NaN);
+
+assert.sameValue(nf.format(), resultNaN);
+assert.sameValue(nf.format(undefined), resultNaN);

test/intl402/NumberFormat/prototype/format/this-value-not-numberformat.js

@@ -16,6 +16,6 @@ invalidTargets.forEach(target => {
   assert.throws(
     TypeError,
     () => fn.call(target),
-    `Calling format getter on ${target} should throw a TypeError.`
+    `Calling format getter on ${String(target)} should throw a TypeError.`
   );
 });

test/intl402/NumberFormat/prototype/formatToParts/this-value-not-numberformat.js

@@ -16,6 +16,6 @@ invalidTargets.forEach(target => {
   assert.throws(
     TypeError,
     () => fn.call(target),
-    `Calling formatToParts on ${target} should throw a TypeError.`
+    `Calling formatToParts on ${String(target)} should throw a TypeError.`
   );
 });

test/intl402/NumberFormat/prototype/resolvedOptions/this-value-not-numberformat.js

@@ -16,6 +16,6 @@ invalidTargets.forEach(target => {
   assert.throws(
     TypeError,
     () => fn.call(target),
-    `Calling resolvedOptions on ${target} should throw a TypeError.`
+    `Calling resolvedOptions on ${String(target)} should throw a TypeError.`
   );
 });