Add ValidationHelperTest.php

tests/Unit/Helper/ValidationHelperTest.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Unit\Helper;
+
+use PHPUnit\Framework\TestCase;
+
+require_once __DIR__ . '/../../../application/helpers/validation_helper.php';
+
+class ValidationHelperTest extends TestCase {
+    public function testValidateDateTimeReturnsTrueOnValidValue()
+    {
+        $this->assertTrue(validate_datetime(date('Y-m-d H:i:s')));
+    }
+
+    public function testValidateDateTimeReturnsFalseOnInvalidValue()
+    {
+        $this->assertFalse(validate_datetime('invalid'));
+    }
+}