1 files changed, 65 insertions, 1 deletions
diff --git a/spec/frontend/locale/index_spec.js b/spec/frontend/locale/index_spec.js
index d65d7c195b2..a08be502735 100644
--- a/spec/frontend/locale/index_spec.js
+++ b/spec/frontend/locale/index_spec.js
@@ -1,5 +1,5 @@
 import { setLanguage } from 'helpers/locale_helper';
-import { createDateTimeFormat, languageCode } from '~/locale';
+import { createDateTimeFormat, formatNumber, languageCode } from '~/locale';
 
 describe('locale', () => {
   afterEach(() => setLanguage(null));
@@ -27,4 +27,68 @@ describe('locale', () => {
       expect(dateFormat.format(new Date(2015, 6, 3))).toBe('July 3, 2015');
     });
   });
+
+  describe('formatNumber', () => {
+    it('formats numbers', () => {
+      expect(formatNumber(1)).toBe('1');
+      expect(formatNumber(12345)).toBe('12,345');
+    });
+
+    it('formats bigint numbers', () => {
+      expect(formatNumber(123456789123456789n)).toBe('123,456,789,123,456,789');
+    });
+
+    it('formats numbers with options', () => {
+      expect(formatNumber(1, { style: 'percent' })).toBe('100%');
+      expect(formatNumber(1, { style: 'currency', currency: 'USD' })).toBe('$1.00');
+    });
+
+    it('formats localized numbers', () => {
+      expect(formatNumber(12345, {}, 'es')).toBe('12.345');
+    });
+
+    it('formats NaN', () => {
+      expect(formatNumber(NaN)).toBe('NaN');
+    });
+
+    it('formats infinity', () => {
+      expect(formatNumber(Number.POSITIVE_INFINITY)).toBe('∞');
+    });
+
+    it('formats negative infinity', () => {
+      expect(formatNumber(Number.NEGATIVE_INFINITY)).toBe('-∞');
+    });
+
+    it('formats EPSILON', () => {
+      expect(formatNumber(Number.EPSILON)).toBe('0');
+    });
+
+    describe('non-number values should pass through', () => {
+      it('undefined', () => {
+        expect(formatNumber(undefined)).toBe(undefined);
+      });
+
+      it('null', () => {
+        expect(formatNumber(null)).toBe(null);
+      });
+
+      it('arrays', () => {
+        expect(formatNumber([])).toEqual([]);
+      });
+
+      it('objects', () => {
+        expect(formatNumber({ a: 'b' })).toEqual({ a: 'b' });
+      });
+    });
+
+    describe('when in a different locale', () => {
+      beforeEach(() => {
+        setLanguage('es');
+      });
+
+      it('formats localized numbers', () => {
+        expect(formatNumber(12345)).toBe('12.345');
+      });
+    });
+  });
 });