From adcba39052e48be5920ec5427a24af4baac22f57 Mon Sep 17 00:00:00 2001
From: Andrew Patton <andrew@acusti.ca>
Date: Sun, 28 Apr 2024 17:03:25 -0700
Subject: [PATCH] Add tests for getMonthFromDate util

---
 packages/date-picker/src/utils.test.ts | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/packages/date-picker/src/utils.test.ts b/packages/date-picker/src/utils.test.ts
index 5931c4eb..348e0367 100644
--- a/packages/date-picker/src/utils.test.ts
+++ b/packages/date-picker/src/utils.test.ts
@@ -2,8 +2,26 @@ import { describe, expect, it } from 'vitest';
 
 import { getMonthFromDate, getMonthNameFromMonth } from './utils.js';
 
+const INVALID_DATE = new Date('');
+
 describe('@acusti/date-picker', () => {
     describe('utils', () => {
+        describe('getMonthFromDate', () => {
+            it('returns the correct month digit for a post-unix epoch month', () => {
+                expect(getMonthFromDate(new Date(1970, 0, 8))).toBe(0); // january 8, 1970
+                expect(getMonthFromDate(new Date(1971, 11, 1))).toBe(23); // november 1, 1971
+            });
+
+            it('returns the correct month digit for a pre-unix epoch month', () => {
+                expect(getMonthFromDate(new Date(1969, 11, 31))).toBe(-1); // december 31, 1969
+                expect(getMonthFromDate(new Date(1968, 3, 30))).toBe(-21); // april 30, 1968
+            });
+
+            it('returns NaN for an Invalid Date)', () => {
+                expect(getMonthFromDate(INVALID_DATE)).toBe(NaN);
+            });
+        });
+
         describe('getMonthNameFromMonth', () => {
             it('returns the correct month name for a post-unix epoch month', () => {
                 expect(
@@ -13,12 +31,12 @@ describe('@acusti/date-picker', () => {
 
             it('returns the correct month name for a pre-unix epoch month', () => {
                 expect(
-                    getMonthNameFromMonth(getMonthFromDate(new Date(1865, 5, 19))),
+                    getMonthNameFromMonth(getMonthFromDate(new Date(1865, 5, 2))),
                 ).toBe('June');
             });
 
             it('returns an empty string if given NaN (e.g. if dealing with an Invalid Date)', () => {
-                expect(getMonthNameFromMonth(getMonthFromDate(new Date('')))).toBe('');
+                expect(getMonthNameFromMonth(getMonthFromDate(INVALID_DATE))).toBe('');
             });
         });
     });