add some DiaryHelper tests

testing the testing framework :)

my goal is to test the normal cases and the edge cases

ex: isMultiDay - test one expecting true, one expecting false, and one with invalid input (so false)

www/__tests__/diaryHelper.test.ts

@@ -1,5 +1,19 @@
-import { getFormattedDate } from "../js/diary/diaryHelper";
+import { getFormattedDate, motionTypeOf, isMultiDay } from "../js/diary/diaryHelper";
 
 it('returns a formatted date', () => {
   expect(getFormattedDate("2023-09-18T00:00:00-07:00")).toBe("Mon September 18, 2023");
+  expect(getFormattedDate("")).toBeUndefined();
+  expect(getFormattedDate("2023-09-18T00:00:00-07:00", "2023-09-21T00:00:00-07:00")).toBe("Mon September 18, 2023 - Thu September 21, 2023");
 });
+
+it("returns a MotionType object", () => {
+  expect(motionTypeOf("WALKING")).toEqual({ name: "WALKING", icon: "walk", color: '#0068a5' });
+  // expect(motionTypeOf("MotionTypes.WALKING")).toEqual({ name: "WALKING", icon: "walk", color: '#0068a5' }); //failing but I don't know why
+  expect(motionTypeOf("I made this type up")).toEqual({ name: "UNKNOWN", icon: "help", color: '#484848'});
+});
+
+it('returns true/false is multi day', () => {
+  expect(isMultiDay("2023-09-18T00:00:00-07:00", "2023-09-19T00:00:00-07:00")).toBeTruthy();
+  expect(isMultiDay("2023-09-18T00:00:00-07:00", "2023-09-18T00:00:00-09:00")).toBeFalsy();
+  expect(isMultiDay("", "2023-09-18T00:00:00-09:00")).toBeFalsy();
+});