From fc137c09b3c8e4a435cd358c24fa19bb085fde36 Mon Sep 17 00:00:00 2001
From: einhornimmond <info@einhornimmond.de>
Date: Tue, 4 Jun 2024 13:25:18 +0200
Subject: [PATCH] add additional tests for edge cases

---
 backend/src/util/utilities.test.ts | 59 ++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 backend/src/util/utilities.test.ts

diff --git a/backend/src/util/utilities.test.ts b/backend/src/util/utilities.test.ts
new file mode 100644
index 000000000..5c193d5a8
--- /dev/null
+++ b/backend/src/util/utilities.test.ts
@@ -0,0 +1,59 @@
+import { getFirstDayOfPreviousNMonth } from './utilities' // Adjust the path as necessary
+
+describe('getFirstDayOfPreviousNMonth', () => {
+  test('should calculate 3 months prior to March 31, 2024', () => {
+    const startDate = new Date(2024, 2, 31) // March 31, 2024 (month is 0-indexed)
+    const monthsAgo = 3
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2023, 11, 1)) // December 1, 2023
+  })
+
+  test('should handle end of month correctly, January 31, 2024', () => {
+    const startDate = new Date(2024, 0, 31) // January 31, 2024
+    const monthsAgo = 1
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2023, 11, 1)) // December 1, 2023
+  })
+
+  test('should handle leap year, March 1, 2024', () => {
+    const startDate = new Date(2024, 2, 1) // March 1, 2024
+    const monthsAgo = 1
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2024, 1, 1)) // February 1, 2024
+  })
+
+  test('should handle leap year, February 29, 2024', () => {
+    const startDate = new Date(2024, 1, 29) // February 29, 2024 (leap year)
+    const monthsAgo = 12
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2023, 1, 1)) // February 1, 2023
+  })
+
+  test('should handle end of year transition, January 1, 2024', () => {
+    const startDate = new Date(2024, 0, 1) // January 1, 2024
+    const monthsAgo = 1
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2023, 11, 1)) // December 1, 2023
+  })
+
+  test('should handle a large number of months ago, December 15, 2024', () => {
+    const startDate = new Date(2024, 11, 15) // December 15, 2024
+    const monthsAgo = 24
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2022, 11, 1)) // December 1, 2022
+  })
+
+  test('should handle start of month correctly, February 1, 2024', () => {
+    const startDate = new Date(2024, 1, 1) // February 1, 2024
+    const monthsAgo = 1
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2024, 0, 1)) // January 1, 2024
+  })
+
+  test('should handle middle of month correctly, February 14, 2024', () => {
+    const startDate = new Date(2024, 1, 14) // February 14, 2024
+    const monthsAgo = 3
+    const result = getFirstDayOfPreviousNMonth(startDate, monthsAgo)
+    expect(result).toEqual(new Date(2023, 10, 1)) // November 1, 2024
+  })
+})