Add test for handling STDIN per suggestion during code review

Author: rodrigoprimo

src/Standards/Generic/Sniffs/Files/LowercasedFilenameSniff.php

@@ -44,7 +44,7 @@ public function process(File $phpcsFile, $stackPtr)
     {
         $filename = $phpcsFile->getFilename();
         if ($filename === 'STDIN') {
-            return $phpcsFile->numTokens; // @codeCoverageIgnore
+            return $phpcsFile->numTokens;
         }
 
         $filename          = basename($filename);

src/Standards/Generic/Tests/Files/LowercasedFilenameUnitTest.php

@@ -9,6 +9,9 @@
 
 namespace PHP_CodeSniffer\Standards\Generic\Tests\Files;
 
+use PHP_CodeSniffer\Files\DummyFile;
+use PHP_CodeSniffer\Ruleset;
+use PHP_CodeSniffer\Tests\ConfigDouble;
 use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
 
 /**
@@ -76,4 +79,28 @@ public function getWarningList()
     }//end getWarningList()
 
 
+    /**
+     * Test the sniff bails early when handling STDIN.
+     *
+     * @return void
+     */
+    public function testStdIn()
+    {
+        $config            = new ConfigDouble();
+        $config->standards = ['Generic'];
+        $config->sniffs    = ['Generic.Files.LowercasedFilename'];
+
+        $ruleset = new Ruleset($config);
+
+        $content = '<?php ';
+        $file    = new DummyFile($content, $ruleset, $config);
+        $file->process();
+
+        $this->assertSame(0, $file->getErrorCount());
+        $this->assertSame(0, $file->getWarningCount());
+        $this->assertCount(0, $file->getErrors());
+
+    }//end testStdIn()
+
+
 }//end class