Add test for negative zero inputs

test/intl402/DurationFormat/prototype/format/negative-zero.js

@@ -0,0 +1,58 @@
+// Copyright (C) 2024 André Bargull. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-Intl.DurationFormat.prototype.format
+description: >
+  Test format method with negative zero as the input.
+locale: [en-US]
+includes: [testIntl.js]
+features: [Intl.DurationFormat]
+---*/
+
+const units = [
+  "years",
+  "months",
+  "weeks",
+  "days",
+  "hours",
+  "minutes",
+  "seconds",
+  "milliseconds",
+  "microseconds",
+  "nanoseconds",
+];
+
+for (let unit of units) {
+  let positiveZero = {
+    [unit]: +0,
+  };
+
+  let negativeZero = {
+    [unit]: -0,
+  };
+
+  let auto = new Intl.DurationFormat("en", {[unit + "Display"]: "auto"});
+
+  assert.sameValue(
+    auto.format(positiveZero),
+    "",
+    `+0 ${unit} is the empty string when display is "auto"`
+  );
+
+  assert.sameValue(
+    auto.format(negativeZero),
+    "",
+    `-0 ${unit} is the empty string when display is "auto"`
+  );
+
+  let always = new Intl.DurationFormat("en", {[unit + "Display"]: "always"});
+
+  let expected = formatDurationFormatPattern(always, positiveZero);
+
+  assert.sameValue(
+    always.format(negativeZero),
+    expected,
+    `-0 ${unit} produces the same output as +0 ${unit} when display is "always"`
+  );
+}