test: add switzerland test

tests/.pest/snapshots/Countries/SwitzerlandTest/it_can_calculate_swiss_holidays.snap

@@ -0,0 +1,38 @@
+[
+    {
+        "name": "Neujahr",
+        "date": "2024-01-01"
+    },
+    {
+        "name": "Berchtoldstag",
+        "date": "2024-01-02"
+    },
+    {
+        "name": "Karfreitag",
+        "date": "2024-03-29"
+    },
+    {
+        "name": "Ostermontag",
+        "date": "2024-04-01"
+    },
+    {
+        "name": "Auffahrt",
+        "date": "2024-05-09"
+    },
+    {
+        "name": "Pfingstmontag",
+        "date": "2024-05-20"
+    },
+    {
+        "name": "Bundesfeier",
+        "date": "2024-08-01"
+    },
+    {
+        "name": "Weihnachtstag",
+        "date": "2024-12-25"
+    },
+    {
+        "name": "Stephanstag",
+        "date": "2024-12-26"
+    }
+]

tests/Countries/SwitzerlandTest.php

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+<?php
+
+namespace Spatie\Holidays\Tests\Countries;
+
+use Carbon\CarbonImmutable;
+use Spatie\Holidays\Holidays;
+
+it('can calculate swiss holidays', function () {
+    CarbonImmutable::setTestNowAndTimezone('2024-01-01');
+
+    $holidays = Holidays::for(country: 'ch')->get();
+
+    expect($holidays)
+        ->toBeArray()
+        ->not()->toBeEmpty();
+
+    expect(formatDates($holidays))->toMatchSnapshot();
+});