1 files changed, 14 insertions, 0 deletions
diff --git a/spec/frontend/lib/utils/datetime_utility_spec.js b/spec/frontend/lib/utils/datetime_utility_spec.js
index 9eb5587e83c..5b1fdea058b 100644
--- a/spec/frontend/lib/utils/datetime_utility_spec.js
+++ b/spec/frontend/lib/utils/datetime_utility_spec.js
@@ -653,3 +653,17 @@ describe('differenceInSeconds', () => {
     expect(datetimeUtility.differenceInSeconds(startDate, endDate)).toBe(expected);
   });
 });
+
+describe('differenceInMilliseconds', () => {
+  const startDateTime = new Date('2019-07-17T00:00:00.000Z');
+
+  it.each`
+    startDate                               | endDate                                           | expected
+    ${startDateTime.getTime()}              | ${new Date('2019-07-17T00:00:00.000Z')}           | ${0}
+    ${startDateTime}                        | ${new Date('2019-07-17T12:00:00.000Z').getTime()} | ${43200000}
+    ${startDateTime}                        | ${new Date('2019-07-18T00:00:00.000Z').getTime()} | ${86400000}
+    ${new Date('2019-07-18T00:00:00.000Z')} | ${startDateTime.getTime()}                        | ${-86400000}
+  `('returns $expected for $endDate - $startDate', ({ startDate, endDate, expected }) => {
+    expect(datetimeUtility.differenceInMilliseconds(startDate, endDate)).toBe(expected);
+  });
+});