diff --git a/test/formatters.test.js b/test/formatters.test.js
new file mode 100644
index 0000000..b6f07c4
--- /dev/null
+++ b/test/formatters.test.js
@@ -0,0 +1,50 @@
+import {toDatetimeLocal} from '../src/utils/formatters'
+
+test('toDatetimeLocal should format date object into YYYY-MM-DDThh:mm', () =>{
+    // common dates
+    let year = 2020;
+    let monthList = [2, 10];
+    let dayList = [1, 19]; // 1 to 12
+    let hourList = [1, 12];
+    let minutesList = [1, 30];
+    let secondsList = [0, 30];
+    let millisecondsList = [0, 100];
+    for(let i = 0; i < 2; i++){
+        let month = monthList[i] - 1; // 0 to 11
+        let date = new Date(year, month, dayList[i], hourList[i],
+            minutesList[i], secondsList[i], millisecondsList[i]);
+        let yearFormat = year.toString();
+        let monthFormat = monthList[i].toString().padStart(2, '0');
+        let dayFormat = dayList[i].toString().padStart(2, '0');
+        let hourFormat = hourList[i].toString().padStart(2, '0');
+        let minutesFormat = minutesList[i].toString().padStart(2, '0');
+        let dateFormat = toDatetimeLocal(date);
+        expect(dateFormat).toBe(`${yearFormat}-${monthFormat}-${dayFormat}T${hourFormat}:${minutesFormat}`);
+    }
+    
+    // common strings
+    let day = 15;
+    let hour = 12;
+    let dateString = '2020-06-'+ day.toString() + 'T' +
+         hour.toString().padStart(2, '0') + ':00:00.000Z';
+    var offset = new Date().getTimezoneOffset() / 60;
+    hour += -offset;
+    if(hour >= 24){
+        day++;
+        hour -= 24;
+    }
+    else if(hour < 0){
+        day--;
+        hour += 24;
+    }
+    let dateFormat = toDatetimeLocal(dateString);
+    expect(dateFormat).toBe('2020-06-'+ day.toString() + 'T' + 
+        hour.toString().padStart(2, '0') + ':00');
+
+    // invalid parameter
+    expect(() => toDatetimeLocal(2020)).toThrow(Error);
+    expect(() => toDatetimeLocal('2020')).toThrow(Error);
+    expect(() => toDatetimeLocal('19/11/2020')).toThrow(Error);
+    expect(() => toDatetimeLocal(undefined)).toThrow(Error);
+    expect(() => toDatetimeLocal(-1)).toThrow(Error);
+})