Correctly name test class files

tests/CsvTest.php

@@ -0,0 +1,33 @@
+<?PHP
+/**
+ * This script contains tests for the home page.
+ *
+ * @author Joshua Ramon Enslin <joshua@jrenslin.de>
+ */
+declare(strict_types = 1);
+
+// phpcs:disable
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test class for the start page.
+ */
+final class CsvTest extends TestCase {
+
+    /**
+     * Test for HTML output.
+     *
+     * @return void
+     */
+    public function testHTMLOutput():void {
+
+        include __DIR__ . "/../public/csv.php";
+        $output = $this->getActualOutput();
+
+        self::assertIsString($output);
+        ob_clean();
+
+    }
+
+}