diff --git a/test/unit/core_utils_spec.js b/test/unit/core_utils_spec.js
index 41a16a0ed..f8fb8da16 100644
--- a/test/unit/core_utils_spec.js
+++ b/test/unit/core_utils_spec.js
@@ -22,6 +22,7 @@ import {
   isAscii,
   isWhiteSpace,
   log2,
+  numberToString,
   parseXFAPath,
   recoverJsURL,
   stringToUTF16HexString,
@@ -182,6 +183,21 @@ describe("core_utils", function () {
     });
   });
 
+  describe("numberToString", function () {
+    it("should stringify integers", function () {
+      expect(numberToString(1)).toEqual("1");
+      expect(numberToString(0)).toEqual("0");
+      expect(numberToString(-1)).toEqual("-1");
+    });
+
+    it("should stringify floats", function () {
+      expect(numberToString(1.0)).toEqual("1");
+      expect(numberToString(1.2)).toEqual("1.2");
+      expect(numberToString(1.23)).toEqual("1.23");
+      expect(numberToString(1.234)).toEqual("1.23");
+    });
+  });
+
   describe("isWhiteSpace", function () {
     it("handles space characters", function () {
       expect(isWhiteSpace(0x20)).toEqual(true);