add test for CommandFactory

Author: Alexsey-VR

tests/CommandFactoryTest.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Differ\tests;
+
+use PHPUnit\Framework\TestCase;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\CoversMethod;
+use Differ\CommandFactory;
+use Differ\CommandLineParser;
+use Differ\FilesDiffCommand;
+use Differ\DisplayCommand;
+
+#[CoversClass(CommandFactory::class)]
+#[CoversClass(CommandLineParser::class)]
+#[CoversClass(FilesDiffCommand::class)]
+#[CoversClass(DisplayCommand::class)]
+class CommandFactoryTest extends TestCase
+{
+    #[CoversFunction(CommandFactory::class, 'getCommand')]
+    public function testGetCommand()
+    {
+        $fileHandler = fopen(__DIR__ . "/../fixtures/docopt.txt", 'r');
+        $fileData = [];
+        while (($docopt[] = fgets($fileHandler, 4096)) !== false);
+        fclose($fileHandler);
+        $docopt = implode("\n", $fileData);
+
+        $commandFactory = new CommandFactory($docopt);
+
+        // Test for CommandLineParse
+        $this->assertInstanceOf(CommandLineParser::class, $commandFactory->getCommand('parse'));
+
+        // Test for FileDiffCommand
+        $this->assertInstanceOf(FilesDiffCommand::class, $commandFactory->getCommand('difference'));
+
+        // Test for DisplayCommand
+        $this->assertInstanceOf(DisplayCommand::class, $commandFactory->getCommand('show'));
+
+        // Test for undefined command
+        $this->assertNull($commandFactory->getCommand('undefined'));
+    }
+}