support custom fields for invoices (#3077)

tests/Entity/InvoiceMetaTest.php

@@ -0,0 +1,41 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Tests\Entity;
+
+use App\Entity\Customer;
+use App\Entity\EntityWithMetaFields;
+use App\Entity\Invoice;
+use App\Entity\InvoiceMeta;
+use App\Entity\MetaTableTypeInterface;
+
+/**
+ * @covers \App\Entity\InvoiceMeta
+ */
+class InvoiceMetaTest extends AbstractMetaEntityTest
+{
+    protected function getEntity(): EntityWithMetaFields
+    {
+        return new Invoice();
+    }
+
+    protected function getMetaEntity(): MetaTableTypeInterface
+    {
+        return new InvoiceMeta();
+    }
+
+    public function testSetEntityThrowsException()
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected instanceof Invoice, received "App\Entity\Customer"');
+
+        $sut = new InvoiceMeta();
+        $sut->setEntity(new Customer());
+    }
+}