diff --git a/src/formaters.spec.ts b/src/formaters.spec.ts
new file mode 100644
index 0000000..b56887a
--- /dev/null
+++ b/src/formaters.spec.ts
@@ -0,0 +1,23 @@
+import { describe, expect, test } from 'vitest'
+import { formatEveDate, formatIsk } from './formaters'
+
+describe('formatIsk', () => {
+    test('Formats ISK correctly', () => {
+        expect(formatIsk(123456789)).toBe('123.456.789,00 ISK')
+    })
+})
+
+describe('formatEveDate', () => {
+    test('Formats EVE date correctly', () => {
+        const date = new Date(Date.UTC(2022, 0, 1, 0, 0))
+        expect(formatEveDate(date)).toBe('2022.1.1 0:0')
+    })
+
+    test('Returns empty string for undefined date', () => {
+        expect(formatEveDate()).toBe('')
+    })
+
+    test('Returns empty string for null date', () => {
+        expect(formatEveDate(null)).toBe('')
+    })
+})
\ No newline at end of file
diff --git a/src/formaters.ts b/src/formaters.ts
index 8216b2b..cef985a 100644
--- a/src/formaters.ts
+++ b/src/formaters.ts
@@ -11,4 +11,4 @@ export const percentFormater = new Intl.NumberFormat("en-US", {
     maximumFractionDigits: 0
 });
 
-export const formatEveDate = (date?: Date) => !date ? '' : `${date.getUTCFullYear()}.${date.getUTCMonth() + 1}.${date.getUTCDate()} ${date.getUTCHours()}:${date.getUTCMinutes()}`;
\ No newline at end of file
+export const formatEveDate = (date?: Date | null) => !date ? '' : `${date.getUTCFullYear()}.${date.getUTCMonth() + 1}.${date.getUTCDate()} ${date.getUTCHours()}:${date.getUTCMinutes()}`;
\ No newline at end of file