diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Arguments.php b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Arguments.php
new file mode 100644
index 0000000..e4121c8
--- /dev/null
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Arguments.php
@@ -0,0 +1,27 @@
+<?php
+
+/*
+ * Copyright (C) 2017  Daniel Siepmann <coding@daniel-siepmann.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+return [
+    'defaultVendor' => [],
+    'customVendor' => [
+        'runtime-set' => 'vendor MyCustomVendor',
+    ],
+];
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/Expected.diff b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/Expected.diff
new file mode 100644
index 0000000..bba47b8
--- /dev/null
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/Expected.diff
@@ -0,0 +1,16 @@
+--- tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/InputFileForIssues.php
++++ PHP_CodeSniffer
+@@ -1,4 +1,5 @@
+ <?php
++namespace MyCustomVendor\ExtName\Controller;
+
+ /*
+  * Copyright (C) 2017  Daniel Siepmann <coding@daniel-siepmann.de>
+@@ -21,6 +22,6 @@
+
+ use Tx_Extbase_Mvc_Controller_ActionController;
+
+-class Tx_ExtName_Controller_Frontendcontroller extends Tx_Extbase_Mvc_Controller_ActionController
++class Frontendcontroller extends Tx_Extbase_Mvc_Controller_ActionController
+ {
+ }
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Expected.json b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/Expected.json
similarity index 100%
rename from tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Expected.json
rename to tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/Expected.json
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/InputFileForIssues.php b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/InputFileForIssues.php
similarity index 100%
rename from tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/InputFileForIssues.php
rename to tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/customVendor/InputFileForIssues.php
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Expected.diff b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/Expected.diff
similarity index 88%
rename from tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Expected.diff
rename to tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/Expected.diff
index c9b6ec6..72e354f 100644
--- a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/Expected.diff
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/Expected.diff
@@ -1,4 +1,4 @@
---- tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/InputFileForIssues.php
+--- tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/InputFileForIssues.php
 +++ PHP_CodeSniffer
 @@ -1,4 +1,5 @@
  <?php
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/Expected.json b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/Expected.json
new file mode 100644
index 0000000..a720806
--- /dev/null
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/Expected.json
@@ -0,0 +1,24 @@
+{
+    "files": {
+        "InputFileForIssues.php": {
+            "errors": 1,
+            "messages": [
+                {
+                    "column": 7,
+                    "fixable": true,
+                    "line": 24,
+                    "message": "Legacy class definitions are not allowed; found \"Tx_ExtName_Controller_Frontendcontroller\". Wrap your class inside a namespace.",
+                    "severity": 5,
+                    "source": "Typo3Update.LegacyClassnames.MissingNamespace.legacyClassname",
+                    "type": "ERROR"
+                }
+            ],
+            "warnings": 0
+        }
+    },
+    "totals": {
+        "errors": 1,
+        "fixable": 1,
+        "warnings": 0
+    }
+}
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/InputFileForIssues.php b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/InputFileForIssues.php
new file mode 100644
index 0000000..ec7a09e
--- /dev/null
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/LegacyClassnames/MissingNamespaceSniff/defaultVendor/InputFileForIssues.php
@@ -0,0 +1,26 @@
+<?php
+
+/*
+ * Copyright (C) 2017  Daniel Siepmann <coding@daniel-siepmann.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+use Tx_Extbase_Mvc_Controller_ActionController;
+
+class Tx_ExtName_Controller_Frontendcontroller extends Tx_Extbase_Mvc_Controller_ActionController
+{
+}