Test case created for the github issue #27866

Author: bunyamin-gc

lib/internal/Magento/Framework/Filesystem/Test/Unit/Io/FileTest.php

@@ -0,0 +1,45 @@
+<?php
+namespace Magento\Framework\Filesystem\Test\Unit\Io;
+
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\Filesystem\Io\File;
+use PHPUnit\Framework\TestCase;
+
+class FileTest extends TestCase
+{
+    protected function setUp()
+    {
+
+    }
+
+    private function getTmpDir()
+    {
+        $tmpDir = '/tmp/magento-' . \microtime(true);
+        if (!\file_exists($tmpDir)) {
+            \mkdir($tmpDir, 0777, true);
+        }
+        return $tmpDir;
+    }
+
+    /**
+     * To cover the issue on GitHub: #27866
+     * @test
+     * @throws LocalizedException
+     */
+    public function read_should_copy_the_source_file_to_the_given_file_resource()
+    {
+        $content = \mt_rand();
+        $sourceFileName = "source-file.txt";
+        $tmpDir = $this->getTmpDir();
+        \file_put_contents("{$tmpDir}/{$sourceFileName}", $content);
+
+        $file = new File();
+        $targetFileName = "target-file.txt";
+        $targetFileHandle = \fopen("{$tmpDir}/{$targetFileName}" , 'w');
+        $file->cd($tmpDir);
+        $result = $file->read($sourceFileName, $targetFileHandle);
+
+        $targetContent = file_get_contents("{$tmpDir}/{$targetFileName}");
+        $this->assertEquals($content, $targetContent);
+    }
+}