add basic testing suite

tests/verifyAgainstStubsTest.php

@@ -0,0 +1,22 @@
+<?php declare(strict_types=1);
+use PHPUnit\Framework\TestCase;
+
+const ABSPATH = __DIR__ . "/../";
+const WPINC = "wp-includes";
+
+require_once __DIR__ . "/../pg4wp/db.php";
+
+final class verifyAgainstStubsTest extends TestCase
+{
+    const STUBS_DIRECTORY = __DIR__ . '/stubs';
+
+    public function test_verify_against_stubs()
+    {
+        $files = array_diff(scandir(self::STUBS_DIRECTORY), array('.', '..'));
+        foreach($files as $file) {
+            $data = json_decode(file_get_contents(self::STUBS_DIRECTORY . "/" . $file), true);
+            $this->assertSame(pg4wp_rewrite($data['mysql']), $data['postgresql']);
+        }
+
+    }
+}