Add tests for "Intl NumberFormat v3" proposal (#3307)

* Add tests for "Intl NumberFormat v3" proposal

This patch is intended to cover only one aspect of the proposal for
ECMA402: the "interpret strings as decimals" feature.

* fixup! Add tests for "Intl NumberFormat v3" proposal

test/intl402/NumberFormat/prototype/format/value-decimal-string.js

@@ -0,0 +1,24 @@
+// Copyright (C) 2021 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-number-format-functions
+description: >
+  Intl.NumberFormat.prototype.format converts its argument (called value) to a
+  number using ToIntlMathematicalValue.
+features: [Intl.NumberFormat-v3]
+locale: [en-US]
+---*/
+
+var nf = new Intl.NumberFormat('en-US');
+
+// The value 100,000 should only be interpreted as infinity if the input is the
+// string "Infinity".
+assert.sameValue(nf.format('100000'), '100,000');
+// The value -100,000 should only be interpreted as negative infinity if the
+// input is the string "-Infinity".
+assert.sameValue(nf.format('-100000'), '-100,000');
+
+assert.sameValue(nf.format('1.0000000000000001'), '1.0000000000000001');
+assert.sameValue(nf.format('-1.0000000000000001'), '1.0000000000000001');
+assert.sameValue(nf.format('987654321987654321'), '987,654,321,987,654,321');
+assert.sameValue(nf.format('-987654321987654321'), '-987,654,321,987,654,321');

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

@@ -19,7 +19,9 @@ const toNumberResults = [
   [true, 1],
   [false, 0],
   ['42', 42],
-  ['foo', NaN]
+  ['foo', NaN],
+  ['Infinity', Infinity],
+  ['-Infinity', -Infinity]
 ];
 
 const nf = new Intl.NumberFormat();