Add tests for keep-trailing-zeros proposal

features.txt

@@ -19,6 +19,10 @@ Intl.Locale-info
 # https://github.com/tc39/proposal-intl-numberformat-v3
 Intl.NumberFormat-v3
 
+# Keep trailing zeros in Intl.NumberFormat and Intl.PluralRules
+# https://github.com/tc39/proposal-intl-keep-trailing-zeros
+keep-trailing-zeros
+
 # Legacy RegExp features
 # https://github.com/tc39/proposal-regexp-legacy-features
 legacy-regexp

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

@@ -0,0 +1,78 @@
+// Copyright (C) 2025 Mozilla Foundation. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: pending
+description: >
+  Intl.NumberFormat.prototype.format converts its argument (called value) to a
+  number using ToIntlMathematicalValue, and retains trailing zeros during formatting.
+features: [Intl.NumberFormat-v3, keep-trailing-zeros]
+locale: [en-US]
+---*/
+
+const nf = new Intl.NumberFormat('en-US', { maximumFractionDigits: 20 });
+
+assert.sameValue(nf.format('0'), '0');
+assert.sameValue(nf.format('1'), '1');
+assert.sameValue(nf.format('0.0'), '0.0');
+assert.sameValue(nf.format('1.0'), '1.0');
+assert.sameValue(nf.format('10.0'), '10.0');
+assert.sameValue(nf.format('0.10'), '0.10');
+assert.sameValue(nf.format('0.010'), '0.010');
+assert.sameValue(nf.format('.10'), '0.10');
+assert.sameValue(nf.format('.0'), '0.0');
+assert.sameValue(nf.format('00.0'), '0.0');
+assert.sameValue(nf.format('001'), '1');
+assert.sameValue(nf.format('-0.00'), '-0.00');
+assert.sameValue(nf.format('-.00'), '-0.00');
+assert.sameValue(nf.format('3.100'), '3.100');
+assert.sameValue(nf.format('6.000000'), '6.000000');
+assert.sameValue(nf.format('1.230e1'), '12.30');
+assert.sameValue(nf.format('1.230e-2'), '0.0123');
+
+// Default maximumfractionDigits is 3
+const nf2 = new Intl.NumberFormat('en-US', { minimumFractionDigits: 1 });
+
+assert.sameValue(nf2.format('1'), '1.0');
+assert.sameValue(nf2.format('1.00'), '1.00');
+assert.sameValue(nf2.format('1.000000'), '1.000');
+
+const nf3 = new Intl.NumberFormat('en-US', {
+  minimumSignificantDigits: 2,
+  maximumSignificantDigits: 4,
+});
+
+assert.sameValue(nf3.format('1'), '1.0');
+assert.sameValue(nf3.format('1.0'), '1.0');
+assert.sameValue(nf3.format('1.00'), '1.00');
+assert.sameValue(nf3.format('0.00'), '0.00');
+assert.sameValue(nf3.format('.00'), '0.00');
+assert.sameValue(nf3.format('1.000000'), '1.000');
+
+const pf = new Intl.NumberFormat('en-US', {
+  style: 'percent',
+  maximumFractionDigits: 10,
+});
+
+assert.sameValue(pf.format('1.0'), '100%');
+assert.sameValue(pf.format('1.00'), '100%');
+assert.sameValue(pf.format('0.50'), '50%');
+assert.sameValue(pf.format('0.5000'), '50.00%');
+
+const sf = new Intl.NumberFormat('en-US', { notation: 'scientific' });
+
+assert.sameValue(sf.format('0.1'), '1E-1');
+assert.sameValue(sf.format('0.01'), '1E-2');
+assert.sameValue(sf.format('0.01200'), '1.200E-2');
+assert.sameValue(sf.format('120.0'), '1.200E2');
+
+const spf = new Intl.NumberFormat('en-US', {
+  style: 'percent',
+  notation: 'scientific',
+  maximumFractionDigits: 10,
+});
+
+assert.sameValue(spf.format('0.0'), '0.0E0%');
+assert.sameValue(spf.format('1.0'), '1.0E2%');
+assert.sameValue(spf.format('1.00'), '1.00E2%');
+assert.sameValue(spf.format('0.50'), '5.0E1%');
+assert.sameValue(spf.format('0.5000'), '5.000E1%');