fix(tests): isolate databases in memory and reject persistent connections

tests/bootstrap.php

@@ -0,0 +1,16 @@
+<?php
+
+// Set every environment source before Laravel or Dotenv can read the local .env.
+foreach ([
+    'APP_ENV' => 'testing',
+    'DB_CONNECTION' => 'sqlite',
+    'DB_DATABASE' => ':memory:',
+    'DB_URL' => 'null',
+    'APP_CONFIG_CACHE' => __DIR__.'/../bootstrap/cache/phpunit-config.php',
+] as $key => $value) {
+    putenv($key.'='.$value);
+    $_ENV[$key] = $value;
+    $_SERVER[$key] = $value;
+}
+
+require __DIR__.'/../vendor/autoload.php';