Deduplicate crypto gateway tests

tests/Unit/Support/CryptoTest.php

@@ -0,0 +1,70 @@
+<?php
+
+namespace MintyPHP\Tests\Unit\Support;
+
+use MintyPHP\Support\Crypto;
+use PHPUnit\Framework\TestCase;
+
+final class CryptoTest extends TestCase
+{
+    protected function setUp(): void
+    {
+        if (!defined('APP_CRYPTO_KEY')) {
+            define('APP_CRYPTO_KEY', str_repeat('ab', 32));
+        }
+    }
+
+    public function testIsConfiguredReturnsTrueWhenKeyIsSet(): void
+    {
+        self::assertTrue(Crypto::isConfigured());
+    }
+
+    public function testEncryptDecryptRoundTrip(): void
+    {
+        $plaintext = 'client-secret-for-sso';
+        $encrypted = Crypto::encryptString($plaintext);
+
+        self::assertNotSame($plaintext, $encrypted);
+        self::assertSame($plaintext, Crypto::decryptString($encrypted));
+    }
+
+    public function testEncryptProducesDifferentCiphertextEachTime(): void
+    {
+        $plaintext = 'same-settings-value';
+
+        self::assertNotSame(
+            Crypto::encryptString($plaintext),
+            Crypto::encryptString($plaintext)
+        );
+    }
+
+    public function testDecryptThrowsOnInvalidOrTamperedPayload(): void
+    {
+        $encrypted = Crypto::encryptString('secret');
+        $tampered = substr($encrypted, 0, 5) . 'Z' . substr($encrypted, 6);
+
+        try {
+            Crypto::decryptString('garbage-data');
+            self::fail('Expected invalid payload to throw.');
+        } catch (\RuntimeException) {
+        }
+
+        try {
+            Crypto::decryptString(base64_encode('{}'));
+            self::fail('Expected malformed payload to throw.');
+        } catch (\RuntimeException) {
+        }
+
+        $this->expectException(\RuntimeException::class);
+        Crypto::decryptString($tampered);
+    }
+
+    public function testEncryptEmptyStringProducesMalformedPayloadOnDecrypt(): void
+    {
+        $encrypted = Crypto::encryptString('');
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('malformed');
+        Crypto::decryptString($encrypted);
+    }
+}