Rework tests structure. Upgrade codeception to 2.5.3. Merge params configuration into app configuration.

common/tests/unit/db/mysql/QueryBuilderTest.php

@@ -0,0 +1,16 @@
+<?php
+namespace common\tests\unit\db\mysql;
+
+use common\db\mysql\QueryBuilder;
+use common\tests\unit\TestCase;
+use Yii;
+
+class QueryBuilderTest extends TestCase {
+
+    public function testBuildOrderByField() {
+        $queryBuilder = new QueryBuilder(Yii::$app->db);
+        $result = $queryBuilder->buildOrderBy(['dummy' => ['first', 'second']]);
+        $this->assertEquals("ORDER BY FIELD(`dummy`,'first','second')", $result);
+    }
+
+}