Try this

Author: jrfnl

VariableAnalysis/Tests/BaseTestCase.php

@@ -9,19 +9,17 @@
 class BaseTestCase extends TestCase {
   const STANDARD_NAME = 'VariableAnalysis';
   const SNIFF_NAME = 'VariableAnalysis.CodeAnalysis.VariableAnalysis';
+  const SNIFF_FILES = [__DIR__ . '/../Sniffs/CodeAnalysis/VariableAnalysisSniff.php'];
 
-  public function prepareLocalFileForSniffs($sniffFiles, $fixtureFile) {
+  public function prepareLocalFileForSniffs($fixtureFile) {
     $config            = new Config();
     $config->cache     = false;
     $config->standards = [self::STANDARD_NAME];
     $config->sniffs    = [self::SNIFF_NAME];
     $config->ignored   = [];
 
     $ruleset = new Ruleset($config);
-    if (! is_array($sniffFiles)) {
-      $sniffFiles = [$sniffFiles];
-    }
-    $ruleset->registerSniffs($sniffFiles, [], []);
+    $ruleset->registerSniffs(self::SNIFF_FILES, [], []);
     $ruleset->populateTokenListeners();
     if (! file_exists($fixtureFile)) {
       throw new \Exception('Fixture file does not exist: ' . $fixtureFile);
@@ -43,10 +41,6 @@ public function getErrorLineNumbersFromFile(LocalFile $phpcsFile) {
     return $this->getLineNumbersFromMessages($phpcsFile->getErrors());
   }
 
-  public function getSniffFiles() {
-    return [__DIR__ . '/../../VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php'];
-  }
-
   public function getFixture($fixtureFilename) {
     return __DIR__ . '/CodeAnalysis/fixtures/' . $fixtureFilename;
   }