1 files changed, 40 insertions, 0 deletions
diff --git a/js/src/tests/non262/Intl/NumberFormat/bigint-int64.js b/js/src/tests/non262/Intl/NumberFormat/bigint-int64.js
new file mode 100644
index 0000000000..7b670d0873
--- /dev/null
+++ b/js/src/tests/non262/Intl/NumberFormat/bigint-int64.js
@@ -0,0 +1,40 @@
+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+
+// Ensure the int64_t optimization when formatting a BigInt value works correctly by testing with
+// various integers around the (u)int[32,64] limits.
+
+const limits = {
+    int32: {
+        min: -0x80000000n,
+        max:  0x7FFFFFFFn,
+    },
+    uint32: {
+        min: 0n,
+        max: 0xFFFFFFFFn
+    },
+    int64: {
+        min: -0x8000000000000000n,
+        max:  0x7FFFFFFFFFFFFFFFn,
+    },
+    uint64: {
+        min: 0n,
+        max: 0xFFFFFFFFFFFFFFFFn
+    },
+};
+
+const nf = new Intl.NumberFormat("en", {useGrouping: false});
+
+const diff = 10n;
+
+for (const int of Object.values(limits)) {
+    for (let i = -diff; i <= diff; ++i) {
+        let n = int.min + i;
+        assertEq(nf.format(n), n.toString());
+
+        let m = int.max + i;
+        assertEq(nf.format(m), m.toString());
+    }
+}
+
+if (typeof reportCompare === "function")
+    reportCompare(true, true);