added test for filesDiffCommand

Author: Alexsey-VR

tests/FilesDiffCommandTest.php

@@ -0,0 +1,64 @@
+<?php
+
+namespace Differ;
+
+use PHPUnit\Framework\TestCase;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\CoversMethod;
+use Differ\FileReader;
+
+#[CoversClass(FilesDiffCommand::class)]
+#[CoversClass(FileReader::class)]
+#[CoversMethod(FilesDiffCommand::class, 'setFileReader')]
+#[CoversMethod(FilesDiffCommand::class, 'execute')]
+class FilesDiffCommandTest extends TestCase
+{
+    private $fileNames;
+
+    protected function setUp(): void
+    {
+        $this->fileNames = [
+            "FILE1" => __DIR__ . "/../file1.json",
+            "FILE2" => __DIR__ . "/../file2.json"
+        ];
+    }
+
+    public function testSetFileReader()
+    {
+        $diffCommand = new FilesDiffCommand();
+
+        $this->assertInstanceOf(
+            FilesDiffCommand::class,
+            $diffCommand->setFileReader(new FileReader()));
+    }
+
+    public function testExecute()
+    {
+        $cmdLineParser = $this->createConfiguredStub(
+            CommandLineParser::class,
+            [
+                'getFileNames' => $this->fileNames
+            ]
+        );
+
+        $diffCommand = new FilesDiffCommand();
+
+        $resultContent = $diffCommand->setFileReader(new FileReader())
+                                 ->execute($cmdLineParser)
+                                 ->getFilesContent();
+
+        $this->assertStringEqualsFile(
+            __DIR__ . "/../fixtures/filesContent.txt",
+            $resultContent
+        );
+
+        $resultDiffs = $diffCommand->setFileReader(new FileReader())
+                                 ->execute($cmdLineParser)
+                                 ->getFilesDiffs();
+
+        $this->assertStringEqualsFile(
+            __DIR__ . "/../fixtures/filesDiffs.txt",
+            $resultDiffs
+        );
+    }
+}