Add tests

src/DateUtils.ts

@@ -102,6 +102,21 @@ export function formatFullDate(date: Date, showTwelveHour = false, showSeconds =
     });
 }
 
+/**
+ * Formats dates to be compatible with attributes of a `<input type="date">`. Dates
+ * should be formatted like "2020-06-23" (formatted according to ISO8601)
+ *
+ * @param date The date to format.
+ * @returns The date string in ISO8601 format ready to be used with an `<input>`
+ */
+export function formatDateForInput(date: Date): string {
+    const year = `${date.getFullYear()}`.padStart(4, "0");
+    const month = `${date.getMonth() + 1}`.padStart(2, "0");
+    const day = `${date.getDate()}`.padStart(2, "0");
+    const dateInputValue = `${year}-${month}-${day}`;
+    return dateInputValue;
+}
+
 export function formatFullTime(date: Date, showTwelveHour = false): string {
     if (showTwelveHour) {
         return twelveHourTime(date, true);

src/components/views/messages/JumpToDatePicker.tsx

@@ -19,20 +19,13 @@ import React, { useState, FormEvent } from "react";
 import { _t } from "../../../languageHandler";
 import Field from "../elements/Field";
 import { RovingAccessibleButton, useRovingTabIndex } from "../../../accessibility/RovingTabIndex";
+import { formatDateForInput } from "../../../DateUtils";
 
 interface IProps {
     ts: number;
     onDatePicked: (dateString: string) => void;
 }
 
-function formatDateForInput(date: Date): string {
-    const year = date.getFullYear();
-    const month = `${date.getMonth() + 1}`.padStart(2, "0");
-    const day = `${date.getDate()}`.padStart(2, "0");
-    const dateInputValue = `${year}-${month}-${day}`;
-    return dateInputValue;
-}
-
 const JumpToDatePicker: React.FC<IProps> = ({ ts, onDatePicked }: IProps) => {
     const date = new Date(ts);
     const dateInputDefaultValue = formatDateForInput(date);

test/utils/DateUtils-test.ts

@@ -19,6 +19,7 @@ import {
     formatRelativeTime,
     formatDuration,
     formatFullDateNoDayISO,
+    formatDateForInput,
     formatTimeLeft,
     formatPreciseDuration,
     formatLocalDateShort,
@@ -126,6 +127,15 @@ describe("formatFullDateNoDayISO", () => {
     });
 });
 
+describe("formatDateForInput", () => {
+    it.each([["1993-11-01"], ["1066-10-14"], ["0571-04-22"], ["0062-02-05"], ["99999-09-09"]])(
+        "should format %s",
+        (dateString: string) => {
+            expect(formatDateForInput(new Date(dateString))).toBe(dateString);
+        },
+    );
+});
+
 describe("formatTimeLeft", () => {
     it.each([
         [0, "0s left"],